How to multiply two 2 digit numbers quickly everybody else: • Do the tens and then the units" This guy: • First find the average • Next raise to the 2 = a(^2) • Subtract the number you first thought of from the average • Raise to the 2 = b(^2) • a(^2) subtract b(2) • Simmer on a low heat for 15 to 20 minutes and add salt to taste • Serve with fava beans and a nice Chianti"
This seems like a good trick, as long as the average of the two numbers is some very round number like 20. But who out there really finds 58x58 to be any easier of a multiplication than 57x59?
are you familiar with the math trick used in the book 'cheaper by the dozen'? it had to do with memorizing squares up to 25. I read it long ago and the idea has stayed with me despite not fully understanding the full process.
Is the trick with the x² of numbers in the 50 range the squere root of each number and the 25 from the 5 u ad whatever the unit value so we have 5²=25+4=29 and 4²=16 there for 2916 am i right ir way off?
And if these numbers are NOT equaly spread around average or average is not a "nice" number ? Example: 17*24 = ? 17*24 = 10*20 + 7*4 + (7*2+1*4)*10 = 200 + 28 + 180 = 408 Much faster and easier ...
difference from the average, not between the two numbers, which is 2, square it to 4, 729 - 4 = 725 and you have your answer. The formula is just (a-b) * (a+b) = a^2 - b^2, where a is the average and b is difference from average. Also why does yt suggest 9 year old videos to us?
How to multiply two 2 digit numbers quickly
everybody else:
• Do the tens and then the units"
This guy:
• First find the average
• Next raise to the 2 = a(^2)
• Subtract the number you first thought of from the average
• Raise to the 2 = b(^2)
• a(^2) subtract b(2)
• Simmer on a low heat for 15 to 20 minutes and add salt to taste
• Serve with fava beans and a nice Chianti"
It's easier to find 20^2 and 3^2 rather than 17x23.
right when he said square i was like, duuuhhhhhhhhh...
This seems like a good trick, as long as the average of the two numbers is some very round number like 20.
But who out there really finds 58x58 to be any easier of a multiplication than 57x59?
In that case why not do 60x60-60-60-58-58-1?
The difference of 58 from 25 is 33 so thats 3300. Difference from 50 is 8 whose square is 64. So 58 squared is 3364. So 57x59= 3363. Simples.
61 x 59= (60+1)(60-1) and using the multiplication of brackets you result in 3600 + 60 - 60 -1 = 3600-1 =3599. If anyone wants a proof.
are you familiar with the math trick used in the book 'cheaper by the dozen'? it had to do with memorizing squares up to 25. I read it long ago and the idea has stayed with me despite not fully understanding the full process.
I just checked in ten secs 216x216 - 225 = 201 x 231. This workshop good.
Is the trick with the x² of numbers in the 50 range the squere root of each number and the 25 from the 5 u ad whatever the unit value so we have 5²=25+4=29 and 4²=16 there for 2916 am i right ir way off?
And if these numbers are NOT equaly spread around average or average is not a "nice" number ?
Example: 17*24 = ?
17*24 = 10*20 + 7*4 + (7*2+1*4)*10 = 200 + 28 + 180 = 408
Much faster and easier ...
Works best if both numbers are odd, or both numbers are even.
How should it work if the two numbers are different ( one is Even number and another one is Odd number)
what if the average is 79... wouldnt it be bettter to actually calculate the product rather than actually calculating the squares?
How i do math is if 23 x 17 then i do 23 x 10 and 23 x 5 sum it up so 230 and 115 so 345 and then sum the rest which is two so 391
Student: Why do I have to study notable products? Where will I apply that in my life?
Me: Quick, give me two two-digit numbers!
What if they are the same numbers will it be the same method
It's just difference of squares which is (a-x)(a+x)=a^2-x^2
Limited opportunity to use but very nice nonetheless
Seems The first example took 45 seconds not 5, the classical method takes as much.
this is basically (x+y)(x-y) stuff but you fail to apply here
17 x 10 = 170, 17x20 = 340, 17 x 3 = 51, 340 + 51 = 391
omg i only wait for skipping add and i fond the answer
Too much easy tricks.
The end
Now square that number ...... Click off.
+WottaNoob haahaa Ditto.
u have made it a bit complicated whilst explaining
lets take 17 and 23
17 is 20-3 and 23 is 20+3
so u have it in the form (a+b)*(a-b) = a^2-b^2
c'est incroyable
25*29
average=27
difference=4
27^2-4^2=729-16=713
but the product of numbers ending in 5 and 9 should end with 5 so it doesn't always work
difference from the average, not between the two numbers, which is 2, square it to 4, 729 - 4 = 725 and you have your answer. The formula is just (a-b) * (a+b) = a^2 - b^2, where a is the average and b is difference from average. Also why does yt suggest 9 year old videos to us?
It's a union
Ok, in my head i multiplied 17x*10(2)340 and 17*3(30+21)51 and got 391 in seconds. The other was too confusing to listen to. Sorry im old school
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