Let T be the time and L be the Labour (Number of people working on the bridge)
T∞ 1/√L (Inverse relationship)
T=K/√L (Constant "K" is introduced once the variation sign (∞) changes to equality (=) sign)
Where T = 75 and L = 9
First, the relationship between these variables is T=225/√L
Therefore, how long it will take 25 people to d it means that we should look for the time.
T= 45 days.