Tuesday, January 19, 2010

Try out this! AMAZING!

WE have all learned that

a2 - b2 = (a + b)(a - b)

But perhaps WE haven't thought about how to use this to do fast mental calculations! See if you can guess how this trick can help you do the following in your head:

43 x 37
78 x 82
36 x 24

Let's do the first one.


43 x 37 = (40 + 3)(40 - 3) = 402 - 32 = 1600 - 9 = 1591.


Practice these, and you'll be able to impress your friends!


WE got all the answers CORRECTLY without using the calculator! Impressive!


Hint: Begin with the BIG number!


Happy trying! (^_^)
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3 comments:

  1. wan amizatul nasyirahJanuary 25, 2010 at 2:43 AM

    Wow! that's fun and amazing guys!

    ReplyDelete
  2. enchantedmathsJanuary 25, 2010 at 6:10 AM

    That's really impressive! Good job for posting this. We think that it will be a great channel to expose children to another approach of solving Mathematical problems that involve big numbers. Keep it up guys! :)

    ReplyDelete
  3. geometricaJanuary 25, 2010 at 6:41 PM

    woww!! this is very imressive..n very interesting indeed and a new way of counting big numbers..we will definately try them later (^_*)

    ReplyDelete

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