If 2+3=95, 4+5=259, 6+7=4913, then 8+9=? Reddit r/theydidthemath

[@bprpmathbasics]

Why do we “keep, change, & flip” when we divide by a fraction? kzbin.info/www/bejne/oqeWnKyCo8SobqMsi=Wz-OQyrcCiiBB0ls

[@agingerredhead9380]

i may be wrong, it’s been a few years but because changing the sign and flipping the fraction are inverse operations and multiplying fractions is pretty eadt

[@reidpattis3127]

If 2+3=5, 4+5=259, and 6+7=4913, then Half Life 3 will be released tomorrow.

[@ThatPicaro]

that's a true statement

[@HenrikMyrhaug]

Nerdy answer: The + doesn't mean addition, it symbolizes some operator that you are trying to figure out.

[@xinpingdonohoe3978]

Obviously you don't know how to count. It isn't 1, 2, 3. It's 1, 2, Alyx.

[@monke7566]

​@@xinpingdonohoe3978actually, it's 1, 2, 2.1, 2.2 and *then* alyx

[@GirishManjunathMusic]

Given that: 2 + 3 = 95 4 + 5 = 259 6 + 7 = 4913 What is 8 + 9? Rewriting the operations as generic operations (denoted here by § because I cannot find the big asterisk on my phone keyboard) 2 § 3 → 95 4 § 5 → 259 6 § 7 → 4913 Observing: 95 ends in 5 = 2 + 3 and begins with 9 = 3² 259 ends in 9 = 4 + 5 and begins with 25 = 5² 4913 ends in 13 = 6 + 7 and begins with 49 = 7² Clearly, the operation is a combination of exponentiation, addition, and concatenation: x § y = y² (concatenation operator) (x + y) Thus: 8 § 9 = 9² (concatenated to) 17 8 § 9 = 8117.

[@eon1311]

Damn good explanation

[@wisteria3032]

the real question is if the second part of the results is a+b or 2a+1.

[@GirishManjunathMusic]

@@wisteria3032 or 2b - 1. In this case it wouldn't change, much like allowing for x § y = (xy + y) (concatenated to) (x + y). If they'd given us any examples where y - x ≠ 1, then we might narrow things down further.

[@fongekyoon9299]

How I got 17 was 9² - 8² 😂

[@stupiditiusmaximus]

It's next to the & symbol.

[@martenkahr3365]

Well, that was a lot easier than what I started doing when I paused. I substituted 2 and 3 with x and y, so it became: If x + y = 95 2x + (x + y) = 259 2y + (2x + y) = 4913 then 4x + 3y = ??? Obviously, nothing sensible came out, because the puzzle was that the + sign represented an arbitrary complex operation, rather than the numbers representing arbitrary integers.

[@TheDIrtyHobo]

I take a strong issue with the way this problem is framed. Namely, using the addition sign when it is clearly not doing the operation of addition. f(a,b) = a + b + 10^floor(log(a+b)+1) * b^2

[@spudhead169]

Yeah, I agree. It shouldn't have used the addition symbol, it should have used a custom symbol.

[@fedorpirulin5128]

2117 is the correct answer. Why not? Let's think about it: Given that: 2 + 3 = 95 4 + 5 = 259 6 + 7 = 4913 What is 8 + 9? We can follow another logic, suppose that at the end of the final number the sum of the two desired numbers, but at the beginning the last two digits of the second number to the power equal to the first number. Thus we get the following logic: 3^2 = 9 => last two digits are 9; 3+2 = 5 then answer is 95 5^4 = 625 => last two digits are 25; 4+5 = 9 then answer is 259 7^6 = 117,649 => last two digits are 49; 6+7 = 13 then answer is 4913 Following this logic we will get another number for 8+9 9^8 = 43,046,721 => last two digits are 21; 9+8 = 17 => answer is 2117 It turns out that these conditions are not enough for this task and there may be many correct answers if they can be justified logically. In my answer I used only the numbers that were given initially.

[@williamroberts5716]

I have come to the conclusion that most math test questions are just exercises in the incorrect use of language or are tricky stupid things that can be resolved if the questions are formatted correctly. It's like card tricks. It doesn't interest me anymore because they're just tricks.

[@thomasmaughan4798]

I have the same conclusion. Tricky use of language. I suspect it helps Google's A.I. calibrate or train itself.

[@methatis3013]

This is not an exam question. This is literally just a riddle

[@williamroberts5716]

@@methatis3013 Exactly. It reminds me of the old riddle if Bob can dig a hole in an a half an hour and Cindy can dig a hole in 45 minutes how long will it take them to dig a hole if they work together? Then you do a bunch of algebra and then a hole is a hole because it doesn't mention the size so the entire question is bogus.

[@emurphy42]

​@@williamroberts5716True as far as it goes, but in that case it may not be intended as a trick question, but just fail to unpack some assumptions. Replace "a hole" with "a hole of some specified size" and the algebra becomes valid. (Exactly what size doesn't matter, just that it's the same across the board, and each person digs out a steady amount of dirt per minute whether or not they have help.)

[@Itsallover57]

Taking math classes as an adult has convinced me that a large part of why people don't like math is because most people that become math teachers are bad at communication.

[@a_diamond]

8117? Edit: yay!

[@thomasjefferson3506]

8+9=17. No amount of preceding false statements change the meaning of the addition operator or the equal sign. Use different notation if you are trying to establish a different kind of relationship: f(8,9) = ???.

[@jamesross1003]

I like your answer to this question and believe that what you came up with is the assumptive answer, but that is with the solver making assumptions. Just because those 3 examples given in the puzzle have a pattern, does not mean that the assumption is correct. There is not enough direction given with the puzzle to actually solve it. The solver could just as well have subbed in variables to these example problems and come up with a different answer. Hence you are making the assumption that this here is the only answer, when there are possibly many or maybe not any plausible solutions at all. Any solver could just as easily made another set of assumptive rules that worked, well maybe not so easy but possible and thus had another valid solution to this puzzle. Since it is not given in the directions of the problem that we are constrained to only real whole numbers and that in order to solve we are required to not follow mathematical conventions, this could just as well have been describing moles in chemistry, ect. I do feel that you reach the conclusion that was originally meant to be found with this puzzle, but must also concede that there could be other valid answers.

[@asdfqwerty14587]

It would be very easy to come up with any solution you'd like. If one wanted to, you could assume that it's quartic function (ie. ax^4+bx^3+cx^2+dx+e), where x is the first number and entirely ignore the 2nd number (ie. 2+ anything = 95, it doesn't matter what the 2nd number is at all), set the final answer to whatever you like and then just solve the system of equations to find the values for abcde to make it correct. There's certainly no way you can prove that that isn't what it should be. .. Or alternatively, you could take the really boring answer since this isn't using correct notation - since it's saying "if 2+3 = 95".. if you take that literally, then anything that comes afterwards is true, because obviously, 2+3 isn't equal to 95, and any statement that says if(false) then.. is going to be a technically true statement. If they wanted to word it the way they intended to they should've said something like f(2, 3) = 95 and so on.

[@jamesross1003]

@@asdfqwerty14587 Yes, that was my point.

[@bjmax3045]

I actually noticed the pattern really quick 6+7=13, and the last digits of the corresponding answer are 1 and 3 I then noticed that the first two digits are 4 and 9, and 49 is 7^2 Then finally noticed that for all the other equations, the answer is the square of the second number, next to the sum of the numbers So, the last one is 8117

[@Ken.-]

It's 6517 0 + 1 = ? (-251) 2 + 3 = 95 (095) 4 + 5 = 259 6 + 7 = 4913 8 + 9 = ? The first number is minus two from the first digit in the first term. 0, 2, 4, 6 The second part alternates between 9 and 5. The last part is the numbers added together. So the last one would be 6517.

[@WLivi]

paused at start to give my read on the problem: f(a,b) = b² concatenated with a+b. f(2,3) = 3² 2+3 = 9 5 f(4,5) = 5² 4+5 = 25 9 f(6,7) = 7² 6+7 = 49 13 f(8,9) = 9² 8+9 = 81 17 if concatenation isn't available to us, then: f(a,b) = (b² × (10 ^ floor(1+log₁₀(a+b)))) + (a+b) f(8,9) = (81 × (10 ^ floor(1+log₁₀(17)))) + 17 = 81 × 10² + 17 = 8117 yes, both of these assume we're dealing with positive integers, primarily because we have been given no information on how this function should operate on other values

[@Jose-Sousa]

f(a,b) = b² concatenated with a*2+1. would also work with the examples given (since in all the examples b = a + 1, so a+b = a*2+1)

[@Jose-Sousa]

Hmmm... my take on this was the following (paused at 0:30): 2+3=95 4+5=259 6+7=4913 I notice that 9, 25 and 49 are squares and actually coincide with the right operand of the expression, so 3^2 = 9, 5^2 = 25 and 7^2 = 49 for the remaining digits, 5, 9 and 13, the first operand doubled plus 1 seems to fit the bill, so 2*2+1 = 5, 4*2+1 = 9, 6*2 + 1 = 13 Putting everything together, generalizing: x+y = (y^2) && (x*2+1) , where && is the concatenation operation So, 8+9 = (9^2) && (8*2+1) = 8117 *unpauses* Well my solution is different but we reach the same result, I guess for all the examples, considering x+y, since y=x+1, then x*2+1 = x + y so our result is identical. But if the question was for 6+9 then result would differ (8113 or 8115)...

[@deltalima6703]

8145 might be more elegant, see if you agree. Y²&&Y²-X² Would be the formula and it fits each example.

[@Jose-Sousa]

@@deltalima6703 Gotta say that I agree, that expression looks really nice as a solution to solving the puzzle. And for the 8+9 the result matches the result obtained from the other proposed/found solutions. So the final result would be the same (8+9=8117) but the way to get to it can be quite different. Now the puzzle becomes: How many solutions can we find to explain/obtain a logical result to the problem.

[@JubeiKibagamiFez]

At least this one had some logic to it.

[@Qeisama]

Before I watched the vid, based on the thumbnail I'd say 8 + 9 = 8117 My order of operation is: a + b = (a x b) + b paired with a + b For example: 2 + 3 = 95 2 + 3 = (2 x 3) + 3 paired with 2 + 3 2 + 3 = 9 paired with 5 = 95 Thus, 8 + 9 = (8 x 9) + 9 paired with 8 + 9 = 81 paired with 17 = 8117

[@suryatejag3821]

Yeee i just did the same thing

[@cortezchavez5891]

The 2nd number squared before the actual answer also works 3²=9,2+3=5 therefore 2+3=95 5²=25,4+5=9 therefore 4+5=259 7²=49, 6+7=13 therefore 6+7=5913 So, 9²=81 and 9+8=17, therefore 9+8=8117 I'm surprised that also works, I didn't even think of that 🤣🤣🤣.

[@melodywolff6346]

Puzzles like this always remind me from some notes I saw of Lewis Carroll. He had various different sequences with the same beginning, but that diverged massively after that. Which highlighted how you never really know how a series will continue, you can just give a best guess. Indeed, the solution here is almost surely the correct one, however, we could interpolate infinitely many polynomials to the first three numbers and get other, "equally valid" solutions.

[@chadd990]

My guess before watching the video: Square the second number in the equation, then place the sum of the two numbers at the end of the square to form a number. a+b=c is the puzzle formula c=[b^2][a+b] (I don't know the correct symbols to represent this) Example: 8+9= [9^2][8+9] = [81][17] = 8117 Let's see how I did

[@Escviitash]

The most common symbol for concatenation is two vertical bar between the values. For this puzzle it would then be a + b = (b^2)||(a+b)

[@chadd990]

@@Escviitash ok, thank you!

[@ghqebvful]

Commenting before watching: what I notice is that the number after the equals sign appears to the the second number squared with the sum of the two numbers appended. (3^2 = 9, 2 + 3 = 5, so the first line has 95); this pattern seems to work for the 3 points of data listed, but it doesn't feel like enough data to feel good about my answer which is 8 + 9 = 8117

[@workhard2belazy]

This is not math, this is pattern recognition.....

[@D-V-O-R-A-K]

Concatenation can be avalid mathematical function

[@Oakeybloke]

Technically pattern recognition is part of maths, as seeing patterns helps to solve problems 🙂 I doubt this is a question for school kids, more of a fun riddle for nerds, like me 😂

[@suryatejag3821]

Another way to find the first two digits: 2+3=95, 2*3=6, 6+second digit (3)=9 Similar for the rest two also 8+9=???? 8+9=??17(17aldready found ) 8*9=72, 72+9=81 Thus the number is:8117

[@AidenHardy596]

Looks like 8117 at first glance The pattern is take the second number ^2 for the first or two digits depending on what it multiplies to Then add the two numbers together normally for the last digit/2 digits 6+7=4913 7^2=49 6+7=13 Put it together 4913

[@DonnyHooterHoot]

If Pi are round, then what color is red? Great explanation!

[@thomasjefferson3506]

PI are round, cornbread are square.

[@flaregod9563]

2+3=95 =3^2 and attach a 2+3 which is 5 to it 4+5=259 =5^2and attach 4+5 which is 9 Same pattern for 8+9 So 9^2 and attach 8+9 to it which is 17 So….8117

[@ThePenguinMan]

this one was easy, solved it in the thumbnail. first digits are the second numbers squared, and the last digits are the numbers added. so 2 + 3 is 3 squared, which is nine, and then 2 + 3 which is 5, so the answer is 95. rinse and repeat you get 8 + 9 being 8117

[@NoahYoshi55]

8117 was my guess after finding the pattern it was completely luck Edit: I was correct

[@TheLuchokpoo]

I just woke up and still sleepy, so I was trying something different and reached the same results. If you do a + b then instead of doing simply b^2 I did a^2 + (a+b) and got the same numbers. Just a curiosity

[@arshiaghafourzadeh6511]

This is because b=a+1 so b^2=(a+1)^2=a^2+2a+1 now a=b+1 so b^2=a^2+a+a+1=a^2+a+b=a^2+(a+b) so you did the same thing from a different perspective

[@Mechanikatt]

Difference of squares a² and b² where a >= b is (a+b)(a-b). Because a and b (example: 3 and 2) differ by only 1, it reduces to (a+b).

[@cstiger4]

I am not fond of those math puzzles. You can give a lot of arbitrary answers and they can all be correct. With polynomial continuation you get the following polynomial from the first 3 pairs: f(x) = 99265/16 - (15387 x)/8 + (2245 x^2)/16 if you then enter 17 for x you get 14057. So in my opinion if you interpret above as f(x) = 95 (for x = 2+3), ... the function that meets this criteria gives you f(17) (17=8+9) = 14057. (and if you just "pick" a 4th number you can find a polynomial that produces that).

[@lochie2804]

Currently 13 seconds into the video, and I feel like I spotted it quite quickly. 2+3=95? 3^2=9, 2+3=5 9 5 4+5=259? 5^2=25, 4+5=9 25 9 6+7=4913? 7^2=49, 6+7=13 49 13 8+9=??? 9^2=81, 8+9=17 Therefore, the answer is 8117

[@raniamuzamel369]

8 + 9= 8117

[@marinecorpswarrior915]

8117 no big explanation needed: just add the two numbers together then square the second number. 8+9=17; 9×9 #81

[@Learning-oe8mc]

My explanation for this question -: 2+3=> 95 4+5=>259 6+7=>4913 8+9=> 8117 =>In first place or position (last nu in addition) square & second position ((first nu in addition ×2)+1) Like In 2+3 => in first position (last nu in addition is 3^2=> 9) & second position (first number in addition is (2×2)+1=> 5) 4+5=(5)^2 (4×2)+1=> 259

[@sundaycorner]

Me just getting it a bit more complicated 😅😅 I thought : - Let the first number be x Let the second number be y So, first digit : (xy)+y second digit: x+y Therefore, equation - (xy)+y ; (x+y) Hope ya' all like it ...... although making the steps more complex..😊😊😊

[@andrinaleong4079]

This is easy. Square the second number and write it down. Add the two numbers and write it after the squared number.

[@meefmeef6254]

plus 1 to the first number and square double second number and minus 1 havent watched yet thats what i think 8117 update im stupid u can just square the second number lol

[@sundown456brick]

havent watched the video yet got 8117 what i did was square the second number of the equation (3, 5, 7 or 9) and put it first then sum the two number (2 & 3, 4 & 5, 6 & 7, 8 & 9) and add (not in the addition way but connect, concatenate, etc) the result in the final of the squared numbers 2 + 3 = 95 2 + 3 = [3², 2 + 3] 2 + 3 = [9, 5] 2 + 3 = 95 (just connect the two values, not add) bad explanation but thats basically what i noticed probably took 2min max very fun !

[@richardtrager7125]

Thought about it for 20 seconds, tried 100-a-b doesn’t work, tried b^a;a+b and realised it’s b^2;a+b. Thus 8117

[@m3m3sis]

yay, i got it before the explanation. Gonna show this to the third class I'm an assistant teacher in. Kids are going to be confused af.

[@dxdux]

I saw a different pattern for the second part: (2 * 3) + 3 = 9 then (4 * 5) + 5 = 25 and then (6 * 7) + 7 = 49, so my solution was (8 * 9) + 9 = 81.

[@bobh6728]

So what would 5+7 be? The last part is 12. But is the first part 7*7=49 or (5+1)*7=42 Both 4912 and 4212 fit the pattern (and lots of other answers are possible). If this is on a test, the answer should be considered correct if the test taker can give a logical explanation for their answer even if it not the “expected” answer.

[@Vyshada]

8117? they just square second numbers and put them in front of a sum result? Why?

[@goldfishglory]

I’m guessing 8117 because 3*3=9 and 2+3=5 making 95. The same rule applies to the other 2. y^2*10+(x+y)

[@Menieres4Life]

I figured it out from the thumbnail and stopped the video during the opening commercial to give my answer, the answer is 8+9=8117

[@flaregod9563]

Got it before even clicking on the video in 10 seconds

[@danniefmr]

Same, you are not special

[@MidnightTheOne]

I got it in -7 seconds, you owe me time

[@rancidblock5615]

@@danniefmr Maybe you both are special

[@flaregod9563]

@@danniefmr ik

[@nicholas930]

So i just noticed the answer is composed of two parts, the two numbers added (2nd half) and the second number to be added, squared (1st half) so by this logic 9^2 = 81 and 8+9 = 17 so 8117

[@klausolekristiansen2960]

I just don't get why you would factor. It takes guesswork, and you may end up with no answer. The quadratic formula always works, and you don't have to guess.

[@F1r1at]

Yeah, it works for 8+9. If we had 7+9, or 5+8, or any other non consecutive numbers there'd be a problem, cause there'd be multiple solutions.

[@a.g.7880]

I figured out the first part, but not the second part.

[@sattvikannadatha2797]

8+9= 8117 ( square of second digit is first number and sum of the 2 digits is second number)

[@IONProd]

I figured it out before you even got to the problem lol. Just sum the numbers and put the square of the 2nd number in front

[@darkflux]

i've not yet watched the video. it is 8117. amirite? Update: just watched the video. i initially had thought it was related to a relative math, like a factor of 2+3 times something to get the result, but it ended up being something much simpler :)

[@mdinventions1763]

I got it without seeing the Sol 😮😂😂❤❤❤❤🎉🎉🎉🎉🎉

[@DikaWolf]

Paused: The answers are all X + Y = {Y * Y} {X + Y} or 8 + 9 ={9 * 9} {8 + 9} = 8117.

[@pegatheetoo1437]

8+9 = 617 ??? I think it's probably wrong ... Just a guess

[@joshuat7171]

9x9=81 9+8=17 8117

[@Medhusalem]

I mean probably not for a 3rd grader, but I found that quite easy.

[@Arvl.]

I was like 5+4=259 which is 9=259 then 6+7 - 3+2 = 8 which is 4913-95 so add both 5077

[@nyandyn]

Next find a finite field and base where addition actually works.

[@Myzner]

I'm weird I did 2+3=5 for ending numbers then noticed the difference was going up by 8 so 16, 24 and the last one had to be 32+49=81

[@dreadhaisler6054]

8117, square the second number and place the sum of the two numbers 🤣

[@muratbaran9775]

answer 8117 it took me just less than 1 minute to understand this

[@Fire_Axus]

just another one of the easy patterns: 8+9=8117

[@DVCH_YT]

Finally something I could solve instantly.😅

[@DavidBrown-zp5vs]

My calculation at start makes it 8117, lets see how wrong my thinking is.

[@AnthonySouls]

8117? I need to look at the answers and video, lol. Last number to the second power with the other numbers added append to the end?

[@MichaelRau-n3e]

Ok i had it after 10 seconds. Where is my prize?

[@NecronHandlee]

My dumbass thought this was a simultaneous equation and that "2" and "3" were just like a and b

[@natsudragneel2640]

Yay I did it right and I almost wanted to not pause the video to try myself but now I feel great😁

[@MrMousley]

Before I watch your video .. 2 + 3 = 5 which is the number at the end of 95 4 + 5 = 9 which is the number at the end of 259 6 + 7 = 13 which is the number at the end of 4913 Then .. 3 x 3 = 9 which is the number at the start of 95 5 x 5 = 25 which is the number at the start of 259 7 x 7 = 49 which is the number at the start of 4913 So .. 8 + 9 is 9 x 9 followed by 8 + 9 which is 8117

[@Sonofzeus07]

I solved this in 3 mins bro Thanks to you actually i watch your vids and love solving puzzels

[@dragonexpert8323]

Figured it out before watching the video. Just want to see the explanation though.

[@eonstar]

(8+9)(9^2) =1781

[@HoldupLetHimCook]

hey wannated to ask if you if i^4 can be a solution for sqr root of x = -1

[@nandkumars.vanamali1336]

I got the same qn

[@ResourcefulNomad]

It could be 12,117 if you go with the next prime instead of the next odd number. 🤔

[@thenetsurferboy]

Maths is a totally different subject from Math

[@aorippedbandaid3711]

Answer is 61317. Reading from the middle term First number of 2^59 is the first number from previous terms operators (2^ + 3) The middle number [(5) of (259)] is the sum of the previous operators (2+3) The last number (9) is the sum of the current operator(4+5) Similarly, for 4913 : 4 from first number of 4+5 9 from sum of 4+5 13 from sum 6+7 Therefore for 8+9: 6 from first number of 6+7 13 as second number from sum of 6+7 17 as sum of 8+9 Resulting in 61317 I did not extrapolate that the 0th term would've been 0+1 since it does not fit my answer

[@eagle32349]

8117, or just 17.

[@legohead2731]

17. Next question

[@Pokemonshorts-wi2eo]

8 added 9 is simply 17

[@a.tsuruya8]

To be honest, these posts would be far less annoying if they simply used the expression f(2,3) = 95

[@hodayfa000h]

Wait so i literally solved it in 2 secs? And it was correct? I am not joking i just looked at 6+7 = 4913 Saw that 7^2 = 49 and that 6+7 = 13 Just assumed the same for the last and did it in 2 secs

[@sasukesuite1]

a "+" b = (a + b) + 100(a+1)b

[@deltalima6703]

8117 took me 35 seconds or so. Wonder what the real answer is.

[@ayeshafatima8737]

8082

[@brockpiano]

my guess before watching is 8117 edit: the only math question i will ever get right

[@ChronicGamer-rl2bo]

It's kinda simple once you think about it but is this really a third grade math problem?

[@James-dc3yt]

If it is it shouldnt be

[@xaiano794]

9+10 = 21

[@danny89620]

It's 17, the other three are just simply incorrect.

[@Vyshada]

It also can be any number BUT 17, since in the examples = clearly means ≠ (Is that how people 'prove' 1=2?)

[@Bruh-uf1si]

"Sir, your IQ is OVER 9 THOUSAND!!!"

[@joustwave6541]

Came here to see if the answer was 8,117

[@meijuta]

I saw the thumbnail, solved it in my head as 8117, then when it said "not 17" on the thumbnail i assumed it was referring to the latter 2 digits; was confused so i watched to see where i went wrong. TL;DR: I got clickbaited

[@pihvi-p2p]

in Chinese, 8+9 means gangsters

[@RoderickEtheria]

8+9=8117.

[@Guiboard]

I think I got it? - - - The first part of the answer involves a multiplication and the second part of the answer is an addition?

[@wjun0131]

819

[@zacharylewis7702]

Just a pattern

[@Raylaobulahu]

156-2.nit what sir please

[@mrmdemeter1]

Haven’t watched the video. Just looked at thumbnail. Answer is 8117

[@ayeshafatima8737]

8072

[@vampyreo2861]

8 + 9 is 17

[@patrickmkiv]

8+9=17 no matter what nonsense is written above.

[@stratos4646]

8117