Exams › SSC CGL (Prelims) › General

Lalit can finish a work in 15 days. Laxman can finish the same work in 25 days. They work together for 5 days. If the rest of the work is finished by Lalit and Deven in 4 days, then in how many days can Deven alone finish the work?

1. 30 days
2. 25 days
3. 21 days
4. 20 days

Correct answer: 20 days

Solution

Lalit’s rate is 1/15 and Laxman’s rate is 1/25, so together they do 8/75 of the work per day. In 5 days they complete 40/75 = 8/15, leaving 7/15. Lalit and Deven finish this in 4 days, so their combined rate is 7/60; subtracting Lalit’s rate 1/15 gives Deven’s rate 1/20, so Deven alone takes 20 days.

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