In How many ways can 5 ladies draw water from 5 taps, assuming the no tap remains unused?
To find: number of ways in which 5 ladies draw water from 5 taps.
Condition: no tap remains unused
The condition given is that no well should remain unused.
So possible number of ways are: $5 \times 4 \times 3 \times 2 \times 1=120$.