ffirs.indd

54 Speed Math for Kids
MULTIPLYING HIGHER NUMBERS
Th ere is no reason why we can’t use 200, 500 and 1,000 as reference
numbers.
To multiply by 200, we multiply by 2 and 100. To multiply by 500,
we multiply by 1,000, and halve the answer. To multiply by 1,000,
we simply write three zeros after the number.
Let’s try some examples.
212 × 212 =
We use 200 as a reference number.
+12
+12
200 212 × 212 =
Both numbers are above the reference number, so we draw the circles
above the numbers. How much above? Twelve and 12, so we write
12 in each circle.
Th ey are plus numbers, so we add crossways.
212 + 12 = 224
We multiply 224 by 2 and by 100.
224 × 2 = 448
448 × 100 = 44,800
Now multiply the numbers in the circles.
12 × 12 = 144
(You must know 12 times 12. If you don’t, you simply calculate the
answer using 10 as a reference number.)