Speed Math for Kids Achieve Their Full Potential

Try using   the reference   numbers 9   and 11  to  multiply    7   by  8.

Let’s   try 9   first.

The numbers are below 9 so we draw the circles below. How much below 9? Two and 1. Write 2 and
1 in the circles. Subtract crossways.

7   −   1   =   6

Multiply    6   by  the reference   number, 9.

6   ×   9   =   54

This    is  our subtotal.

Now multiply    the numbers in  the circles and add the result  to  54.

2   ×   1   =   2

54  +   2   =   56  Answer

This    is  obviously   impractical but it  proves  it  can be  done.

Let’s   try 11  as  a   reference   number.

Seven   is  4   below   11  and 8   is  3   below.  We  write   4   and 3   in  the circles.

Subtract    crossways.

7   −   3   =   4

Multiply    by  the reference   number.

11  ×   4   =   44

Multiply    the numbers in  the circles and add the result  to  44.

4   ×   3   =   12

44  +   12  =   56  Answer

This method will also work if we use 8 or 17 as reference numbers. It obviously makes more sense to
use 10 as a reference number for the calculation as we can immediately call out the answer, 56. Still, it