Halving and doubling
You learn a trick to make multiplying easier: halve one number and double the other.
How to work it out
- Halve the even number and double the other number.
- The answer stays the same, but it is much easier to calculate!
14 × 35 = 2 × 7022 × 70 = 140
24 × 5 = ?
- Halve 24: 12.
- Double 5: 10.
- Now: 12 × 10 = 120.
Another example
16 × 25 = ?
- Halve 16: 8.
- Double 25: 50.
- Now: 8 × 50 = 400.