Multiplication Using Any Reference Number 49
18 + 7 = 25
10 × 25 = 250
Multiply the numbers in the circles and add this to the subtotal:
8 × 7 = 56
250 + 56 = 306
Our completed work should look like this:
+8
+7
10 18 × 17 = 250
- 56
306 Answer
Th is confi rms our fi rst answer. Th ere isn’t much to choose between using
the diff erent reference numbers. It is a matter of personal preference.
Simply choose the reference number you fi nd easier to work with.
MULTIPLYING NUMBERS ABOVE AND BELOW 20
Th e third possibility is if one number is above and the other below 20.
+14
20 18 × 34 =
–2
We can either add 18 to 14 or subtract 2 from 34, and then multiply
the result by our reference number:
34 – 2 = 32
32 × 20 = 640