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A builds a wall in 2 hours and B breaks the same wall due to which A takes 4 hours to complete/ build the wall. In what time, B break the full wall.

A builds a wall in 2 hours and B breaks the same wall due to which A takes 4 hours to complete/ build the wall. In what time, B break the full wall. Correct Answer 4 hours

Given

Time taken by A to build a wall = 2 hours

Time taken by A to build a wall when B break the wall simultaneously = 4 hours

Calculation

Wall build by A in 1 hour, when B not break the wall = 1/2

Wall build by A in 1 hour, when B break the wall simultaneously = 1/4

Let the wall break by B is x hours

(1/2) - (1/x) = (1/4)

⇒ (1/2) - (1/4) = (1/x)

⇒ (2 - 1)/4 = 1/x

⇒ 1/4 = 1/x

⇒ x = 4

∴ B will take 4 hours to break the wall.

Additional Information

+ sign indicates constructive work

-  sign indicates destructive/destroyed work

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