The pattern behind the list
Look at the last digit of each answer. From 21 × 1 to 21 × 10 it goes like this, and then the same pattern repeats every ten facts all the way up to 21 × 40:
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 0
Working out big facts
You do not need to learn all 40 facts by heart. Use the method for the 21 times table instead: Split 21 into 20 and 1: work out the 20s and the 1s, then add them.
Split 21 into 20 and 1. 20 × 40 = 800 and 1 × 40 = 40, so 21 × 40 = 800 + 40 = 840.
21 × 40 = 800 + 40 = 840