A civil contractor planned to build an over bridge of 3 km distance in 600 days. For this purpose, he employed 90 workers. After 200 days of work, it was observed that only 0.5 km of the bridge was completed. What is the number of extra workers required to complete the work in time?

135

Formula to be used:

⇒ \(\frac{M_1\;×\;D_1}{W_1}\) = \(\frac{M_2\;×\;D_2}{W_2}\)

where, M= No. of men, D = No. of days, W = work done

Calculations:

⇒ \(\frac{90 × 200}{0.5}\) = \(\frac{M × 400}{2.5}\)

⇒ 36000 = M x 160

⇒ M = \(\frac{900}{4}\) = 225

Extra men to be employed = 225 - 90 = 135 men.