This question was previously asked in

IBPS RRB Office Assistant Prelims: 8 August 2021 Shift 1 - Memory Based Paper

- 12 days
- 15 days
- 8 days
- 18 days
- none of these

Option 4 : 18 days

**Given:**

Time taken to complete the work by A = 60 days

Time taken to complete the work by B = 40 days

Remaining work finished by B = 10 days

**Concept used:**

Efficiency = Total work / Time

**Calculation:**

LCM of 60 and 40 = 120 units = Total work

Efficiency of A = 120/60

⇒ 2 units/days

Efficiency of B = 120/40

⇒ 3 units/days

Remaining work completed by B alone = 3 × 10 days = 30 units

So, time taken by A and B together work

⇒ Total work – Work completed by A alone /Efficiency of A and B

⇒ (120 – 30) / (2 + 3)

⇒ (90/5) days

⇒ 18 days

**∴ A leave the work after 18 days**

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