RRB RPF RPSF SI and CONS Model Papers 10 with solutions

Question : 69 of 120

Marks: +1, -0

A and B can complete a piece of work in 30 days, B and C in 20 days, and C and A in 15 days. If all of them work together, the time taken in completing the work will be

10 days
12 days
$12 2/ 3$ days
$13 1 /3$ days

Validate

Solution:

(4) Work done by (A + B) in 1 day =

{1}/{30}

Work done by (B + C) in 1 day

=1/15

On adding,
Work done by 2 (A +B + C) in 1 day

= {1}/{30}+ {1}/{20}+ {1}/{15}

= {2+3+4}/{60}= {9}/{60}= {3}/{20}

∴ Work done by (A + B + C) in 1 day

=3/40

∴ (A + B + C) will do the work in

40/3=13 1/3

days

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