When you’re multiplying by 4, 5 or 20 there are some easy ways to do it.

Multiplying by 4 is the same as multiplying by 2 twice.
Look:
6 x 4 = 6 x 2 x 2 = 24

Multiplying by 5 is the same as multiplying by 10 and then halving.
Look:
32 x 5 = 32 x 10 ÷ 2 = 160

Multiplying by 20 is the same as multiplying by 10 and then doubling.
Look:
6 x 20 = 6 x 10 x 2 = 120