1 Answers
Option 5 : 11.25 minutes
Given:
Pipe C = 50% + Pipe A
Pipe B: Pipe C = 4 : 5
Pipes opened every 5 minutes
Formula:
If time taken by pipe A to fill tank is ‘a’ minutes and by pipe B is ‘b’ minutes then total time taken to fill the tank t ⇒ (1/t) = (1/a) + (1/b)
Calculation:
Let, time taken to fill the tank by pipe A = X
⇒ Pipe C = 0.5X + X
⇒ Pipe C = 1.5X
⇒ Pipe B: Pipe C = 4: 5
⇒ Pipe B = 4 × 1.5X/5
⇒ 1/ 4 = (1/ X) + (5/6X) + (1/1.5X)
⇒ 1/ 4 = (6 + 5 + 4)/(6X)
⇒ 1/ 4 = 15/ 6X
⇒ 6X = 60
⇒ X = 10 minutes
⇒ Time taken by pipe C = 15 (∵ 1.5 × 10 = 15)
⇒ Time taken by pipe B = 6 × 10/5
⇒ Time taken by pipe B = 12 minutes
Calculating units/ minutes for each pipe
LCM for 10, 12 and 15 = 60
⇒ Pipe A = 6 (∵ 60/10 = 6)
⇒ Pipe B = 5 (∵ 60/12 = 5)
⇒ Pipe C = 4 (∵ 60/15 = 4)
Total quantity to be filled = 60 unit
⇒ Units filled by pipe A = 30 (∵ 6 × 5 min = 30)
Remaining Unit = 60 - 30 = 30
⇒ Units filled by pipe B = 25 (∵ 5 × 5 min= 25)
Remaining Unit = 30 - 25 = 5
⇒ Units filled by pipe C = 5 (∵ 4 × 5/4 min= 5)
⇒ Time taken = 5 + 5 + (5/4)
⇒ Time taken = 11.25 minutes
∴ Time taken to fill up the tank is 11.25 minutes