A and B can do a certain work in 6 hours, and A, B and C together take 4 hours to do the same. How long will it take for C alone to accomplish the task?

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SSC CGL 2022 Tier-I Official Paper (Held On : 03 Dec 2022 Shift 2)
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  1. 12 hours
  2. 4 hours
  3. 2 hours
  4. 6 hours

Answer (Detailed Solution Below)

Option 1 : 12 hours
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Detailed Solution

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Given:

A and B can do a certain work in 6 hours

A, B and C together take 4 hours to do the same.

Concept used:

Total work = efficiency of the workers × time taken

Calculation:

Let the total work be 12 units   [LCM of 4 and 6]

So, efficiency of A and B = 12/6 = 2 units/hour

The efficiency of A, B and C = 12/4 = 3 units/hour

So,

Efficiency of C = 3 - 2

⇒ 1 unit/hour

Time to complete the task by C = 12/1

⇒ 12 hours

∴ The required answer is 12.

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