- 12 days
- 15 days
- 10 days
- 8 days

Option 3 : 10 days

**Given **

A can complete the work = 25 days

B can complete the same work = 20 days

**Formula used **

Work = Time × Efficiency

**Calculation **

Let the total work = LCM(25, 20) = 100 unit

Efficiency of A = 100/25 = 4/day

Efficiency of B = 100/20 = 5/day

Both can do work in 10 days together = 9 × 10 = 90 units

C's efficiency = 10/10 = 1/day

A, B and C can complete the whole work = 100/(4 + 5 + 1) = 10 days

**∴ The required answer is 10 days **

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