Multiplication Using Any Reference Number 51
Let’s try it:
50 47 × 45 =
–3
–5
Subtract diagonally:
45 – 3 = 42
Multiply 42 by 100, then divide by 2:
42 × 100 = 4,200
4,200 ÷ 2 = 2,100
Now multiply the numbers in the circles, and add this result to
2,100:
3 × 5 = 15
2,100 + 15 = 2,115
50 47 × 45 = 4,200
–3
–5
2,100
- 15
2,115 Answer
Fantastic. Th at was so easy. Let’s try another:
+3
+7
50 53 × 57 =
Add diagonally, then multiply the result by the reference number
(multiply by 100 and then divide by 2):
57 + 3 = 60
60 × 100 = 6,000