A can do a work in 7 \frac{1}{2} {h} and B can do the same work in 10 \frac{1}{2} h. If they work together for 3 \frac{1}{2} {h}, then what part of the work will be left out?

SSC CHSL 13 Apr 2021 Shift 3 Paper

Section: Quantitative Aptitude

Question : 72 of 100

Marks: +1, -0

A can do a work in

7 \;{1}/{2} {h}

and

B

can do the same work in

10 \;{1}/{2}

h. If they work together for

3 \;{1}/{2} {h}

, then what part of the work will be left out?

Solution:

According to the question,
Total work done by

A

and

B

together in

3 \;{1}/{2} {h}

\;{7}/{2} {h}

=\;{\;{7}/{2}}/{{15}/{2}}+\;{\;{7}/{2}}/{{21}/{2}}=\;{7}/{15}+\;{1}/{3}=\;{7+5}/{15}=\;{12}/{15}

∴

Remaining work

=1-\;{12}/{15}=\;{15-12}/{15}=\;{3}/{15}=\;{1}/{5}

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