Mental Multiplication Math Trick - Multiply numbers in your head near 100

[@robinmathews777]

I’ve been watching all your video series on multiplication and they really helped a lot in improving my multiplication skills! You’re the best math teacher I never had! Thanks so much for these videos..God bless!

[@mrstuartgibbs]

Just starting from no 1 and working my way up.... Thanks tecmath enjoying maths again..

[@GunterJPN]

For those that know algebra, this is basically changing it to multiplying two binomials and using the FOIL method. 105x107 Change that to (100+5)x(100+7) The cross-adding is combining the FOI in the FOIL method. It makes it easy because your First numbers are 100. 10000 + 700 + 500 ---- 11200 So now it’s just the Last number added to that, or 5x7 = 35 11235 is the answer.

[@divermike8943]

Not sure the foil method is easier to do in your head or not. You want to have fewer numbers to hold in sort term memory from mental math. But it's whatever works best for you.

[@GunterJPN]

@@divermike8943 when working with two numbers close to 100, breaking them up like this actually results in fewer numbers to keep in your head, because the numbers you are working with are exactly what you’re looking at in the original problem. That’s the whole point of breaking it down to 100 and something else.

[@tecmath]

sure.

[@McGavel1]

I really love all these - thanks!

[@lorraineday8150]

McGavel1 stupid

[@thelegacyofgaming2928]

@@lorraineday8150 ?

[@deborahovalle-vazquez7229]

Dude thanks for the math cause I'm getting those equations next week and this one

[@Black.cat._]

Thanks for this series, very good teaching :D

[@mathbbn2676]

very good teacher

[@RicochetRita]

Use the "two base" method, where the secondary base is a simple multiple of the main base. For example, use: 20 (main) & 100 (main x5), to multiply 24 by 96 So, the differences become: 24 - 20 = +4 96 - 100 = -4 Now the important bit: Before cross adding, multiply (or divide) one by that base factor, 5. Either: +4 x 5 = +20 or -4 / 5 = -4/5 Using the easier +20 gives: 96 +20 = 116 x 20 (main) = 2320 Now multiply the (unmodified) differences: +4 x -4 = -16 And finish it: 2320 -16 = 2304

[@SurajPal-kx5tr]

109×102=11100

[@RicochetRita]

@@SurajPal-kx5tr +18

[@emiyakiritsugu6329]

I see, so confusing i dont get it at all (I suck at eng.)

[@RicochetRita]

Now, supposing we'd chosen the use the -4/5 difference. It still works, but it's a more difficult choice to do mentally. So, 24 -4/5 = 23 1/5 = 23.2 Since we diminished this difference, we have to multiple by the secondary base of 100: 23.2 x 100 = 2320 Now the rest is the same: +4 x -4 = -16. So, 2320 -16 = 2304

[@sanjayagarwal7243]

Thank you. Amazing tricks.

[@Nerketur]

Doing the math, this will also work with fractions or decimals as long as you do the multiplication correctly. Also, I like how this is recursive Say I wanted to do 120 × 123 Base 100: +21, +23 14300 + 21 × 23 Base 20: +1, +3 24 × 20 = 480 + 3 = 483 So 121 × 123 is 14300 + 483 = 14783 ---- Also possible with 120 as a base, but that is harder for me to do in my head

[@nkaul7691]

Great video

[@DJ-cm3zm]

I learnt a great concept today May 22, 2017 (IST)

[@Farreach]

i like this makes it so much faster atleast if your dealing with factors of 10 ....10, 100, 1000, 10000, and so on so if its 40,010 x 40,020 you would just add 200 to what ever you get by timing 400,300,000 by 4 ....which is 1,601,200,200...so much faster this way than doing it the typical way

[@SussyEgg297]

This really helps me in math kind of hated math.

[@airmen56]

Thanks a lot, great!

[@islandboyw]

What about when you have mixed base like one number base 10 and another base 100?

[@Aliasbaba41]

Better than the other way round I think.

[@abderrahmanechaddou5779]

very amazing thanks very much indeed,

[@tonybarfridge4369]

With 61x50, why not do 61x5x10 instead of x100/2?

[@tewodroswolderufael7198]

very good,

[@jaysingh-dt8rm]

best method 👍

[@abhigyanchandra7820]

you rock .........i used to hate maths [like poop] but you saved me [If i become a pilot I would like to thank you ]

[@MyBigThing2010]

Abhigyan Chandra that's a scary content right there

[@horinamaniapoto3837]

can u line the numbers proply thats what i didnt understand

[@thelegacyofgaming2928]

This method becomes impossible to do in your head once you get to the 150's and higher, or numbers too far apart from each other.

[@siguythetacoguy7438]

Yeah no it’s after 110 sadly 111 multiplied by 115 ain’t 11605

[@123duelist]

@@siguythetacoguy7438 Actually those two numbers work. The answer I got using the method was 12,765, so it works.

[@emiyakiritsugu6329]

Hey what about 640×311 Do i need base 310 or something 😑😏😏

[@prantoshnaha5114]

i got all the answers correct

[@JOHAN5459]

i love so much your math trick..!! :P

[@divermike8943]

Great video. But I wish he would line up, right justify, his digits when doing addition & subtraction

[@xoxomint3780]

I like your multiplication and l hope l will win in the math challenge

[@clintonsealey7504]

Hi I’ve been learning this from your videos I learnt base of 10 an 20 ect then I tried showing my partner, I had done it with numbers like 23 x 28 etc using a base of 20 an ect then she said try 86x 86 an using the formula I couldn’t work it out it didn’t seem to work out the same way an I looked through your vids an couldn’t find you using the same numbers for this does it work out an could you show it doing so ? Thanks

[@anitajoseph6534]

thanks

[@edgarkais2430]

Any trick for number far apart of each other and closeto two different bases. eg. 23x78

[@M1zt_]

Base 20 (I find it easier to pick the base that is close to the lowest number): +3 & +58 78+3 = 81 * 2 = 162*10 = 1620 3*58 = (150+24) = 174 1620 + 174 = 1794.

[@Nerketur]

Could use a base closest to the center of the two Eg: 23 × 78 :base 50 -27, 28 51 × 50 = 5100 ÷ 2 = 2550 -27 × 28 :base 30 negative of 27×28 -3, -2 25 × 20 = 500 500 + 6 = 506 23 × 78 = 2550 - 506 = 2044 Another way you could do it is say "oh, thats the same as 46 × 39", and use base 40, which would be less work

[@emiyakiritsugu6329]

I think all bases r appropriate 13×83, we can use all bases from 10 to 80, it work every base is appropriate for it

[@RickyBlack9999]

Can I request a video you can try to do?

[@ElMrRojo]

108*56=? Same question of "Chetan singh", and 139*144=? Thanks for your videos!

[@jordanlight374]

dont always use the same trick, some maths questions will require different tricks, strategies etc

[@iSupremest]

do 100x56. then just add 8 x 56. just as simple as the method above

[@Nerketur]

139 × 144: Base 100 +39, +44 139 + 44 = 144 + 39 = 183 183 × 100 = 18300 So 139 × 144 is 18300 + 39 × 44 Do the trick again to figure out 39 × 44, with a base of 40, then add that final result to 18300, and you have your answer.

[@thelegacyofgaming2928]

@@Nerketur This does work, however, how would you keep track of this in your head?

[@wenwenchen7062]

Excuses me, l don't understand how you do the 11100?

[@tobenijrvillarente3332]

What about 51x13

[@nhiphan3704]

With this, just 510 + 153

[@pioneeringworks]

There is a reasonable conclusion on this topic in this channel kzbin.info/www/bejne/imnPo4KOobN9h7M

[@dilipkhednah]

It seems to be most of the numbers he uses add up to ten. tried to do 42x45. His was, It didn't work. The answer from his formula came to 2014. But when i used the calculator the answer was 1890. So where am i going wrong. Or it his formula right.

[@Officialsearch21]

use the bases of 50

[@MyBigThing2010]

He's right...you're making a mistake somewhere...use a base close to your equations numbers to simplify.

[@Psychedelian]

42x45. Use base 40 add 2+5 =7 (when both are above the base just add the 'ones' column together for the final digit) and 2 x 5=10 | 42+5=47 or 45+2=47 so 47 x 40 (or 470 x 4)=1880 + 10 = 1890

[@Psychedelian]

Base 50 is 42 (-8)x 45 (-5) , number become 37. 37x50 (or 370x5)= 3700/2 = 1850. Then (-8 x -5) = 40...1850+40=1890. Same answer no matter what base you use.

[@victorsoto2188]

check your multiplication -8 x -5 =40.....2 negatives equal positive 40 42 -5=37 x 100=3700/2=1850+40=1890 hope this helps

[@elserfamily7974]

to awesome!!!!!!!

[@gelics9948]

it's fun 👏👏

[@spidermek5416]

What about if under say 123× 56

[@NoplanKW]

What happen when you have 537*312 ?

[@prantoshnaha5114]

I LOVE UR VIDS ;]

[@keyshajones5352]

C+=Dramp=cClamp O+B C=cSourceryU=cvlamp n.d

[@moulimindset24]

How to slove 243 multiply 823and 127&485

[@julesgardet659]

_’Aigt “_ = 8

[@nguyenbuixuandung8620]

very cool.

[@Thehyperfury]

108*56=?????

[@Officialsearch21]

I used the bases of 50 which was the video before this one. 58 6 108 X 56 108+6= 114 114 x 100=11,400 11,400/2= 5700 --------- 58 x 6 = (I seriously had to break this down)= 6 X 5 = 30 but of course were doing 50 X 6 = 300 then 8 x 6= 48 300+ 48= 348 then we add both together: 5,700 + 348 = 6,048 Thus, 108 x 56 = 6,048.

[@Robin-sc1lf]

Josue... very good... I'd have done the same. It certainly gets much more complicated the larger the difference between the two numbers being multiplied. It is easy if you follow the rule using paper but I'd have got way lost trying to do this calc in my head, which is the principle of this technique. I'd get there but it would be very frustrating.

[@Psychedelian]

Or you could do it the easy way (100x56)+(8x50)+(8x6)=6048.This equates to 5600+400+48. It's good to know more than one way to solve problems. Always use the easiest way. Work smart not hard. I didn't use any base except common sense.

[@jessicaliu5941]

chetan singh near 100

[@christocr]

@Led Zep: problem with that is (I'm not saying it doesn't work) it's too hard to hold all those number in your head. The methods this guy presents minimizes the number you have to try to store in your head. On paper, your method is great. But unless you have a really good memory, it's too many numbers floating in your head. That's always the challenge for me--remembering the sub-calculations. The actual computation is usually pretty simple.

[@revanthukkalam3604]

(x+a)(x+b)

[@baldwinavila9801]

what about 100?

[@m.sureshbabu2927]

How 97 Tim's 36 ?

[@GoffCool]

I'm late but here you go. Base 30 . 97=67 more and 36=6 more. so 97 + 6 or 36 + 67 =103 . 10,30 x 3 =3090 and 67 x 6 =402 . 3090 + 402= *3492*

[@lorraineday8150]

you crazy I already now my time tables

[@moulimindset24]

What bro tell me

[@moulimindset24]

Sir you are vidious really helpful but some problem do not solve for example 49 multiply 87 and you told 55 multiply 56 solve 3050.... Tell me and 13 multiply 69 give to vidious

[@Nerketur]

49 × 87: base 60 - 11, +27 87 - 11 = 76 76 × 60 = 4560 -11 × 27 = -297 49 × 87 = 4560 - 297 = 4263

[@grey2326]

The first answer is the Fibonacci sequence

[@TheRhamza]

5th

[@ethanjennings1729]

Wat Isabella plus Lucy

[@ethanjennings1729]

The same age as the other SIDE is your birthday

[@cricketupdateandcricketpre2883]

103×93 ka trick solution kare

[@roopeshgupta7457]

We are use vedic math

[@manasa9974]

Plz explain this 107*79

[@GoffCool]

I'm late but here you go. Base 70. 107+9 or 79+37 = 116 1160x7= 8120 and 9x37=333 8120+333=8453

[@newsmansuper2925]

105 x 107 = 10700 + 535 = 11235

[@SurajPal-kx5tr]

Savan kumar answer is 105×107=11200

[@newsmansuper2925]

21 x 14 = 280 + 14 = 294

[@newsmansuper2925]

105 x 101 = 10500 + 105 = 10605

[@newsmansuper2925]

104 x 97 = 10400 - 312 = 10088

[@newsmansuper2925]

109 x 102 = 10900 + 218 = 11118

[@barryjackson405]

10400-312. 104x100 less 104x3.

[@exostatics]

95

[@MrTerminalZ]

I have a different way, this is cheating. But my way may be ineffecient, as it took me 20 minutes of staring at a wall to solve 355 * 268.

[@mmjgaming7607]

There is no way to "cheat at math". In fact Arthur Benjamin, famous mathematician, one said that math simply is finding formulas and applying it to different numbers (by the way I very much paraphrased there please see his lecture at Ted X Oxford for the exact words.

[@MyBigThing2010]

How is this "cheating" you are still calculating answers manually. Man I hope you're some dumb kid and not a member of society with a divers license or a job that matters to anyone

[@enzou]

MMJ Gaming yeah he’s my idol I learn some tricks from him ! I learnt the golden ratio from him too

[@enzou]

Dude this guy plays free online games and has no life then says this is cheating

[@cloudplayz7403]

this is the worst video by him as it is 5 years gone but he has only 129,788 views and only 890 likes vs 47 dislikes. BTW I love ur videos very much :D

[@mohammadmasiullah1258]

U r saying so slowly

[@Mrbargais]

How I ended up here from cat videos?

[@ItsUrFav12345]

Mrbargais shut up

[@PK-tn4vs]

this is confusing

[@MyBigThing2010]

parsa kimiaie not really. Maybe you world view the base 10 videos and work your way up. It's ACTUALLY very useful and easy....period is not only me...scroll the comments. ....it's not a freebie...you have to learn it and practice but once you get out in your head you'll easily be doing this in your head with correct answers while others screw up on paper

[@prigaming1735]

2020 anyone

[@TuanNguyen-np8pv]

second :D

[@The310johnny]

First

[@SussyEgg297]

So darn long hurry up already.

[@arkisawesome]

Very bad chanel

[@arkisawesome]

Give a like to my comment if you agree

[@keyshajones5352]

C+=Dramp=cClamp O+B C=cSourceryU=cvlamp n.d

[@tobenijrvillarente3332]

What about 125x15

[@enzou]

benito villarente 1975

[@nirv2796]

benito villarente Multiply by 20 then add half of that

[@keyshajones5352]

C+=Dramp=cClamp O+B C=cSourceryU=cvlamp n.d