Try this:
- Take 15 x 13 for an example.
- Always place the larger number of the two on top in your mind.
- Then draw the shape of Africa mentally so it covers the 15 and the 3 from the 13 below. Those covered numbers are all you need.
- First add 15 + 3 = 18
- Add a zero behind it (multiply by 10) to get 180.
- Multiply the covered lower 3 x the single digit above it the "5" (3x5= 15)
- Add 180 + 15 = 195.
Post a Comment and let us know what you think of this trick!
I find it somewhat diffucult to remember the shape of africa on the rop of my head and put it down. So basiccaly i cant take it any further! any solutions to this?
ReplyDeleteI got another cool math trick. It allows u to multiply numbers by 11. basically yuou pick a number[if this is 4 fun] or take the one in the question. Now seperate the two numbers.[not the 11 the other number] [if its one digit put the digit on the left side.] now take the two numbers and add them together. And put the answer in the middle.Then carry if neccasary. Here is an example. lets x11 by say 27. Now we "open up the number" so now it will look like 2 7. Now lets add 2+7 since those are the two digits in the number. 2+7=9. So now we put 9 in between the 2 and the 7. You now have 297. Now look try it on the calculator and be amazed at how useful this trick is. [note: cant use 3 digit numbers or higher.] maybe i will figure out how to use 3 digit numbers but until then u got this cool amazing multiplication trick
ReplyDeleteAlso, if you multiply a two digit number, where the sum of both digits is a two digit number, you would add the first digit of the sum to the first digit of the original number.
ReplyDeleteFor example - 28 x 11
Separate the 2 8
Add 2 + 8 = 10 - put this answer in the
middle...
So you have 2 1 0 8
Then you add 2 + 1 = 3, so the answer is
3 0 8 = 308