This question was previously asked in

UPSSSC Chakbandi Lekhpal Official Paper 2 (Held on : 30 Sept 2019 Shift 2)

Option 1 : 50

**Given:**

Time is taken by Tap A to fill the tank = 18 mins

Time is taken by Tap B to fill the tank = 36 mins

Time is taken by Tap C to fill the tank = 54 mins

**Concept Used:**

Total Work = Time taken × Efficiency

**Calculation:**

LCM of 18,36, 54 is 108

Total Work = 108 unit

Efficiency of Tap A = 108/18 ⇒ 6 units/min

Efficiency of Tap B = 108/36 ⇒ 3 units/min

Efficiency of Tap C = 108/54 ⇒ 2 units/min

According to the question

Tap A work done for 1 min = 6 units

Tap B work done for 4 min = 4 × (3) ⇒ 12 units

Remaining work = 108 - (12 + 6) ⇒ 90 units

The Time is taken to complete the remaining work by C = 90/2 ⇒ 45 mins

Total time taken to fill the tank = 1 + 4 + 45 ⇒ 50 mins

**∴ The total time (in minutes) required to fill the tank is 50 minutes**

**Note:**

The question was incorrect in the official paper. However, we have changed it and update it accordingly.