Sarthak and Mohan are working on alternate days in a workshop. Sarthak can complete the work in 20 days while Mohan can finish in 25 days. Sarthak works on the 1st day, Mohan on the 2nd day, and so on. How much time (in days) will they take on alternate basis?

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SSC Selection Post 2024 (Higher Secondary Level) Official Paper (Held On: 25 Jun, 2024 Shift 4)
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  1. \(20 \frac{1}{5}\)
  2. \(22 \frac{1}{5}\)
  3. 23
  4. \(22 \frac{1}{3}\)

Answer (Detailed Solution Below)

Option 2 : \(22 \frac{1}{5}\)
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Detailed Solution

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Given:

Sarthak can complete the work in 20 days

Mohan can complete the work in 25 days

Sarthak works on the 1st day, Mohan on the 2nd day, and so on.

Formula used:

Work done by Sarthak in 1 day = 1/20

Work done by Mohan in 1 day = 1/25

Combined work in 2 days = Work done by Sarthak in 1 day + Work done by Mohan in 1 day

Calculation:

Combined work in 2 days = (1/20) + (1/25)

⇒ Combined work in 2 days = (5 + 4) / 100

⇒ Combined work in 2 days = 9/100

Total work = 1

Number of such 2 day cycles required to complete the work:

⇒ Total work / Combined work in 2 days

⇒ 1 / (9/100)

⇒ 100/9 ≈ 11 cycles

Work done in 11 cycles or 22 days = 11 × 9/100 = 99/100

Remaining work = 1 - 99/100 = 1/100

Now, Sarthak complete this work in 20/100 = 1/5.

Total days = 22 1/5.

∴ The correct answer is option (3).

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