Time and Work Practice Test 1 with solutions

Question : 39 of 40

Marks: +1, -0

A, B and C complete a piece of work in 20, 12 and 18 days respectively. They start the work together but A drops out after 4 days and B drops out 2 days before the completion of the work. The work is finished in :

$2 {22}/{25}$ days
$6 {24}/{29}$ days
$5 {24}/{25}$ days
$4 {24}/{25}$ days

Validate

Solution:

Let the work has been finished in t days, then

4 × 1/{20}

+ (t - 2) ×

1/{12}

+ t ×

1/{18}

= 1
⇒

(1/{12}+1/{18}) t - 1/6

1 - 1/5

⇒

5/{36} t

4/5 + 1/6

∴ t =

{29}/{30} × {36}/{5}

{174}/{25}

6 {24}/{25}

days.

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