A tap can fill a tank of 500litres in 3hours30minutes. In how much time will it fill one-fifth of the tank?
Step 1. One-fifth of 500litres of tank =15x500=100litresStep 2. Time taken by the tap o fill 500litres =3hours30min=3.5hours[30min=0.5hour]
Therefore time taken by the tap to fill 1litres =3.5500hoursStep 3. Time taken by the tap to fill 100litres =3.5500x100
Hence time taken by tap to fill one-fifth of the tank is 42minutes