Multiplying by 20, 25, and 30

Multiplying By Twenty

Multiplying by 20 is done in two stages, by 2 and then by 10.


Multiplying By Twenty Five

To multiplying by 25:

Divide the number by 4. Then:
If you have a remainder of 0 then add 00 at the end.
If you have a remainder of 1 then add 25 at the end.
If you have a remainder of 2 then add 50 at the end.
If you have a remainder of 3 then add 75 at the end.

Example: 143 * 25

143 / 4 = 35 remainder: 3

so
143 * 25 = 35 & 75 (for a remainder of 3 add 75 at the end)
143 * 25 = 3575


Multiplying By Thirty

Multiplying by 30 is done in two stages, by 3 and then by 10.