AT A PARTY

At a party surprise your friends with this spectacular way of multiplying large numbers together in your head.

• Suppose you want to multiply 88 by 98.
  
  Not easy,you might think. But with
  VERTICALLY AND CROSSWISE you can give
  the answer immediately, using the same method
  as before.
  
  Both 88 and 98 are close to 100.
  88 is 12 below 100 and 98 is 2 below 100.
  
  You can imagine the sum set out like this:
  
  
  
  
  As before the 86 comes from
  subtracting crosswise: 88 - 2 = 86
  (or 98 - 12 = 86: you can subtract
  either way, you will always get
  the same answer).
  And the 24 in the answer is
  just 12 x 2: you multiply vertically.
  So 88 x 98 = 8624
  
   

This is so easy it is just mental arithmetic.

At A Party

Where there is life there is pattern
and where there is pattern there is
mathematics

John D. Barrow