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Preethi and Rishi together can complete a work in 30 days. And Preethi alone can complete the same work in 60 days. If they started working together but after 10 days Preethi left, then in how many days Rishi will complete the remaining work?

Preethi and Rishi together can complete a work in 30 days. And Preethi alone can complete the same work in 60 days. If they started working together but after 10 days Preethi left, then in how many days Rishi will complete the remaining work? Correct Answer 40 days

Given:

Preethi and Rishi together can complete a work in 30 days

Preethi alone can complete the same work in 60 days

After 10 days Preethi left the work

Formula used:

Number of days = Total work/1 day's work (Efficiency)

Calculation:

Preethi + Rishi → 30 days

Preethi → 60 days

Total work = LCM (30, 60) = 60 unit

1 day's work of (Preethi + Rishi) = 60/30 = 2 unit

1 day's work of Preethi = 60/60 = 1 unit

⇒ 1 day's work of Rishi = 2 - 1 = 1 unit

Given that, they started working together but after 10 days Preethi left

∴ Work completed in 10 days = 10 × 2 = 20 unit

⇒ Remaining work = 60 - 20 = 40 unit

Number of days Rishi takes to complete the remaining work:

Number of days =  Total work/1 day's work (Efficiency)

⇒ 40/1 = 40 days

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