Speed Math for Kids Achieve Their Full Potential

(Marvins-Underground-K-12) #1
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

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