DRDO Multi tasking staff Model paper 8

20 men can build a wall 25 meters long in 4 days
More men work, length of wall built is more. Number of working days increases the length of wall built
So it is a case of direct proportion
Length of a wall built by 30 men in 6 days = 25 × (30 × 6)/(20 × 4) = 56.25 metre