At 2:59 the original challenge did not specify that the numbers had to be in the cells in order. I can arrange them in many different orders, including randomly, making a Magic Square, and spiral. Most such orders will not work. So, it's no wonder people got it wrong!

Ah yes Bureaucracy even in Math

I knew that 3×5 and 5×3 arent equal Why does this thing even exists, it doesnt make sense

The purpose of teaching repeated addition is to ensure that a student understand what is represented by multiplication. The order of the terms doesnt matter for multiplication, and writing "5+5+5" shows that the student clearly understands the concept. The student was marked wrong over linguistic semantics. This isnt education. Its not teaching the student how to think (which they clearly know how to do, given their absolutely correct answer), but instead teaching them to obey. Utterly ridiculous

5 × 3 is three 5s while 3 × 5 is five 3s, both equal 15

7:05 we can prune it on the other side and we wont get the principal square root, i think it can be +-6

I'm pretty sure 5th graders don't know trigonometry even in China

Wow well this makes no fucking sense

There's a half dog that's large and another half dog that's small. What a crappily put together math question.

5:24 111 is closer to 121 (11²) than to 100 (10²). The approximation becomes 11 - 10/22 = 10.545454 . . . (whose square is 111.2066) which is a closer approximation than 10 + 11/20 =10.55 (whose square is 111.3025).

Sqrt(-4) is +-2i, sqrt(-9) is +-3i. All combinations of plus and minusses gives +-6

there is an mathemathical correct anagramm: ELEVEN + TWO = TWLEVE + ONE We know that ELEVEN + TWO costs 11$ + 2$ which is 13$ And since there are the same letters in TWELVE + ONE as in ELEVEN + TWO, we can say that their sums have to be equal. So TWELVE + ONE is also 13$. All we have to do now is to subtract the price for ONE from this sum and get 12$.

cant you just subtract the area of the sector with the area of square and then find thearea of the semicircle and then subtract that with the area we found before?

Why go to all that hassle and unnecessary complication when all you need to do is look at the speedometer? OMG! 🤦

6

Well, it seems my calculation for C) was way too convoluted. Notice how every even figure adds gray triangles and that the set of each other odd number (3,7,11...) with a difference of 4 between 2 consecutive numbers is the number of grey triangles that get added for each even figure. That means that figure 250 can be calculated as 3+4*0+3+4*1+3+4*2+...+3+4*125=3*125+4*(125+124+123+...+1+0)=375+4*125*62=31375

But the students need to be taught and shown that 5×3 is the same as 3×5, (by proving that multiplication is commutative, )so the student could’ve said 5×3 is the same as 3×5 and then her answer would be correct. This is a strategy she would need to know if she was given 600×2 as suggested in one of the comments then she could rewrite the problem as 2×600 and get the answer more quickly than adding 600 “2”s

the formula for any number of rows and same number of columns (the number being "n") is: n*(n^2+1)/2 this comes from the arithmetic sum of all numbers in the whole table where you've N=n^2, but is divided by the number of rows or columns (not both at the same time) as that is how many same sums there are in the sum of all numbers. Thus you've N*(N+1)/2 (geometric sum of all numbers in table), insert n^2 instead of N, divide by n and you've got it. If you want to look it through the biggest number in the square table (the N), just calculate directly through N*(N+1)/2*sqrt(N), as N will always be a square number you always get an integer, but it's easier through the number of rows and columns

You have to make the function look like a fish.

W video, W explanation

So why is the w function gives just x? What does it do to xe^x?

"What the 0.5 dog doing?"

Both video answers are unnecessarily complicated. If 3/8 of the book was read on tues & weds, the 30 pages on mon represent the other 5/8ths. Solution is 8/5 x 30 = 48

I am trying to figure out the remaining minutes of interview time when I ask “can I lick them?”.

What I did was : (1/8 * 3) * 100 | 100% - 37.5% | 30 / 62.5% | 0.48 * 100 = 48 total pages I use this method since all of my assignments are point based and not percentages, so I have to use a calculator to find it.

Well, here's the issue... multiplication is commutative, so 5 x 3 = 15 is the same as 3 x 5 = 15 Even if we are not counting that... Addition Representation: 3 + 3 + 3 + 3 + 3 Grouping: (1+1+1) + (1+1+1) + (1+1+1) + (1+1+1) + (1+1+1) Flattening: 1+1+1+1+1+1+1+1+1+1+1+1+1+1+1 Re-grouping: (1+1+1+1+1) + (1+1+1+1+1) + (1+1+1+1+1) Re-grouping pt2: 5 + 5 + 5 So technically the student is correct.

8 9 14 3

disclaimer: Its obviously -6 BUT: if you read the answer as "-6 OR +6" it's a true statement x=sqrt(-4)*sqrt(-9) x=-6 or x=+6 anyway, still wrong

mental gymnastics, 15 is correct

I solved it the "old" way, same as you, because I'm old.

The issue with the first method is that you don't build abstract intuition by doing it this way, most of the time learning the algorithm first and then deconstructing it helps you learn it better. The black box method basically. Don't understand something? Think of it like a black box. Once you know how to use the black box, disassemble it, you will find smaller black boxes inside, and you will have an intuition on how the larger one works, repeat process until you understand the whole thing. The new method is kinda backwards.

Cool. I used to be REALLY bad at math, now I'm just bad at math.😎👍

Immediately I thought 33

16+11+6+1=34

Wait... They don't teach algebra anymore????

these questions make no sense out of context, but are usually quite easy when you know where they come from. If it was specified this question was in the section of the book about prime factors or exponents it would've basically solved half the puzzle

Jesus - he read a 1/4, he read 1/8 so therefore remaining 5/8 is 30 therefore 8/8 is 48 - how did that take 6min 😳

Adding 5 (3 times) is the same as adding 3 (5 times).

34 is equal to the sum of 1 to 16 divided by 4 (rows, columns) for a 4x4-grid. 65 is equal to the sum of 1 to 25 divided by 5 (rows, columns) for a 5x5-grid. Another way to express the rule behind the "magic".

What you are doing is pure "ganita" not equal to computation or calculation

30 Pages + 1/8= 1//4 This 30 Pages= 1/8 Total Pages: 8x30=240 pages

Choose one cell from each row and one from each column, as per instructed, and note the sum. Start over and repeat, such that no previously selected cell is chosen. Repeat twice, again never selecting a previously chosen cell. You now have four totals. Add up the number in all the cells 1 + 2 + ... + 16, which is ½(16)(17) or 136. But this is four times the average number of the 4-cell selction totals. Therefore, divide 136 by 4, which is the number of groups of 4-cell selections. Answer 34. This method makes the undefended assumption that the four cells selected per the rule always add up to the same number, but if it is accepted then my method will work.

You did not make clear that the lines AD, BE and CF are perpendicular to the sides of the triangle but you assumed this in your proof.

If you take a group of 4 batteries and (worst case scenario) all are dead, which will take 6 tests to determine, you know all remaining batteries will be good and the 7th test will work. Just another approach to getting to 7 tests.

Working with the problem just off the thumbnail: the star is 12, the heart is 21, so the answer is 12+21=33. I found this by realizing that the number at the top is equal to the 2 numbers in the corners and 2 times the middle number on the bottom all added together. Knowing this, I subtracted 7+9 from 40, and then divided the answer by 2 to get the number in the centre on the bottom, 12. From there, it’s just adding 12+9 to get the heart. Now to see how my answer compares to the video answer!

not watching the video, but the answer for the thumbnail is 48, right? 30=5/8. anyways, see you. i just saw this on the fly while watching another video. tell me if im wrong.

P/4 = P-(30+P/8) => p=48

Klein read 3/8 of the book in the last 2 days, read 5/8 on the first day.. 5/8 = 30 8/8 = 48

OH, please! 8 seconds, give or take, it took me. In like 1.5 secs, I had 30 is 5/8 of the book. Divided 30 by 5, multiplied by 8 to get 48. Then I did it again in the other 4 secs to check my answer.

*@ MindYourDecisions* -- The special sums are the same as the Magic Constants as the Magic Squares for each appropriate square of numbers.