← Methods
Repeated Doubling
Doubling is the one piece of arithmetic nobody has to stop and think about. Times four is two doublings, times eight is three.
When it works
One side is 4, 6 or 8 — an even number with a small odd part hiding inside it.
Worked through
37 × 8 = 296
- 37 × 2 = 74Double it.
- 74 × 2 = 148Double it.
- 148 × 2 = 296Double it.
10 problems, every one of them this method.