SSC CPO SI and ASI 2016 Paper

Question : 145 of 200

Marks: +1, -0

A and B can separately finish a piece of work in 20 days and 15 days, respectively. They worked together for 6 days, after which B was replaced by C. If the work was finished in next 4 days, then the number of days in which C alone could do the work is

40 days
60 days
30 days
50 days

Validate

Solution:

(1) A's 1 day’s work

=1/2

B's 1 day's work

= {1}/{15}

(A+B)'s 6 days’ work =

6 ( {1}/{20}+ {1}/{15} )=\ {6 × 35}/{300}= {7}/{10}

A's 4 days' work

= {4}/{20}= {1}/{5}

So, C's 4 days’ work =

(1- {7}/{10}- {1}/{5} )=1- {9}/{10}= {1}/{10}

C's 1 day's work

= {1}/{10×4}= {1}/{40}

Hence, C alone will complete the work in 40 days.

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