Question

There are fifteen pipes to fill water in a tank and Rahul was assigned to the task. Today he forgot to open some pipes and resulted in more time to fill the tank. If the number of pipes he failed to open was 3, what will be the percentage increase in filling time?
1. 15
2. 25
3. 40
4. 50

Answer 1

Correct Answer - Option 2 : 25

Calculation:

Let t be the time to fill the tank and k is the part of the tank filled by a single pipe in one hour (efficiency)

Total tank volume = 15 × t × k = 15kt      ---(1)

3 pipes were failed to open

Total tank volume = 12 × t_new × k = 12kt_new      ---(2)

(1) = (2)  ⇒  15kt = 12ktnew

⇒ t_new = (15/12) × t = 5t/4

Percentage increase = ((5t/4 - t) / t) × 100 

Percentage increase = 25%