Question

Ten identical pipes used to fill water in a tank. Rakesh forgot to open some pipes at the time of filling. It took 25% more time to fill the tank. What is the number of pipes he failed to open?
1. 1
2. 2
3. 3
4. 4

Answer 1

Correct Answer - Option 2 : 2

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 = 10 × t × k = 10kt      ---(1)

p pipes were opened

time taken to fill the tank = (125/100) × t = 1.25 t

Total tank volume = p × t new × k = 1.25pkt     ---(2)

(1) = (2)  ⇒  10kt = 1.25pkt

⇒ p = 8

Number of pipes didn't open was 2.