94 Speed Math for Kids
Write them down and calculate the answers, and then
see if you can do them all in your head. With practice it
becomes easy. Here are the answers:
a) 612 b) 632 c) 18,048 d) 16,464
EASY MULTIPLICATION BY 9
It is easy to use this method to multiply any number from 1 to 1,000
by 9.
Let’s try an example:
76 × 9 =
We use 10 as our reference for 9 and 80 as our reference for 76. We
can rewrite the problem like this:
(10 × 8) 9 × 76 =
–1
–4
–8
We subtract 8 from 76 (76 – 10 = 66, plus 2 is 68). Multiply 68 by
the base reference, 10, which equals 680. Now multiply the numbers
in the original circles, and add the result to 680.
1 × 4 = 4
680 + 4 = 684 Answer
Th e base number is always 10 when you multiply by 9. Let’s try
another.
9 × 486 =
Th e reference numbers are 10 and 490. You always go up to the next
10 for the second reference number. We write it like this:
brent
(Brent)
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