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SSC CHSL 2021 PYQ — Question 57

SSC CHSL - 13 April 2021 - Shift 3 • Quantitative Aptitude • Q57

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A can do a work in 712\frac{1}{2} hours and B can do the same work in 1012\frac{1}{2} hours. If they work together for 312\frac{1}{2} hours, then what part of the work will be left out?

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Correct answer: A

Explanation

The correct answer is option 1 i.e. 15\frac{1}{5}

Time taken by A = 15/2 hours

Time taken by B = 21/2 hours

Let total work = 105 units  [Multiple of 15 and 21]

Work done by A per hour work = 105/(15/2) = 14 units

Work done by B per hour work = 105/(21/2) = 10 units

Their total work in 7/2 hours = (24) × (7/2) = 84 units

Work left = (105 - 84) = 21 units

The remaining work = 21/105 = 1/5