RRB RPF RPSF SI and CONS Model Papers 2 with solutions

Question : 33 of 120

Marks: +1, -0

A, B and C can do a piece of work in 10, 12 and 15 days respectively. A leaves 5 days before the completion of the work and B leaves 2 days after A. The whole work lasts for

7 days
6 days
12 days
13 days

Validate

Solution:

(a) Suppose, the work was finished in x days.
Then, A’s (x – 5) day’s work + B’s (x – 3) day’s work + C’s x day’s work = 1.

⇒ { x - 5 }/ { 10 } + { x - 3 } /{ 12 } + { x }/ { 15 }

= 1 ⇒ 6 ( x - 5 ) + 5 ( x - 3 ) + 4 x = 60

⇒ 6 x - 30 + 5 x - 15 + 4 x = 60

⇒ 15 x = 60 + 30 + 15

⇒ 15 x = 105 ⇒x = 7

days

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