0
That depends on what you mean:
twenty add one fifth is 20 + 1/5 = 20 1/5
twenty, add one fifth (of twenty) is 20 + 1/5 * 20 = 20 + 4 = 24
one twenty-fifth = 4%
1/25:
= 1 ÷ 25
= 0.04 in decimal
= 0.04 * 100%
= 4%
604%
1/5