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#1 This is Cool » How to do mental calculations » 2007-07-12 22:36:19

CyclonEnigma
Replies: 1

This is a simple trick for multiplying

Let say:

39x45

39x4=156
39x5=195

156
  195
_____
1755

Now how about three digit by three digit:

362x284

362x2=724
362x8=2896
362x4=1448

724
2896
   1448
_________
102808

If the multiplication of the first number and the first digit of the second number is a three digit product then most likely the answer is a 5-digit answer

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