Harish and Bimal can complete a task in 20 days. They worked at it for 15 days and then Bimal left. The remaining work was done by Harish alone, in 10 days. Harish alone can complete the entire task in:

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Question

This question was previously asked in

NTPC CBT-I (Held On: 4 Jan 2021 Shift 1)

Answer 1

Given:

No of days taken by Harish and Bimal = 20

Formula used:

No of days taken = Work/Efficiency

Calculation:

Let the total work be = 1

One day work done by Harish and Bimal = 1/20

Work done by Harish and Bimal in 15 days = 1/20 × 15 = 3/4

⇒ Remaining work = 1 - 3/4 = 1/4

Harish did remaining work in 10 days alone.

⇒ One day work done by Harish = 1/4 ÷ 10 = 1/40

∴ Time taken by Harish to do the entire task alone = 1 ÷ 1/40 = 40 days

Shortcut TrickFraction of work done by Harish & Bimal in 15 days = 15/20 = 3/4

The remaining 1/4th (25%) of work was done by Harish in 10 days.

∴ The 100% work would be done by Harish in (10 × 4) 40 days.