A and B together can complete a certain work in 20 days whereas B and C together can complete it in 24 days. If A is twice as good a workman as C, then in what time will B alone do 40% of the same work?

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SSC CGL 2020 Tier-I Official Paper 10 (Held On : 18 Aug 2021 Shift 1)
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  1. 12 days
  2. 10 days
  3. 18 days
  4. 15 days

Answer (Detailed Solution Below)

Option 1 : 12 days
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Detailed Solution

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Given:

A = 2C

A + B in 20 days

B + C in 24 days

Concept used:

Total work = LCM of time taken by the workers

Calculation:

LCM of 20 and 24 is 120

So, efficiency of A and B = 120/20 = 6 and efficiency of B and C = 120/24 = 5

Now 2C + B = 6 and B + C = 5

So, C = 1

B = 4

40% of the work = 120 × 2/5 = 48 units

So, B will take 48/4 = 12 days

∴ B alone do 40% of the same work in 12 days

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Now 2C + B = 6 and B + C = 5

So, C = 1

B = 4

So,

A, B and C = 2, 4, and 1

40% of the work = 120 × 2/5 = 48 units

So, B will take 48/4 = 12 days

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