20 men complete one-third of a work in 20 days. How many

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20 men complete one-third of a work in 20 days. How many more men should be employed to finished the rest of work in 25 more days.?

1. 15
2. 12
3. 18
4. 25

Correct Option: B

Given, M₁ = 20.
M₂ = 20 + k
W₁ = 1/3, W₂ = 1 - 1/3 = 2/3
D₁ = 20 and D₂ = 25
According to the formula,
M₁D₁W₂ = M₂D₂W₁
⇒ 20 x 20 x (2/3) = (20 + k) x 25 x 1/3
⇒ 20 x 20 x (2/3) = (20 + k) x 25/3
⇒ 16 x 2 = 20 + k
∴ k = 32 - 20 = 12