A contractor starts the work with few workers to build a wall in 45 days. After 15 days he saw that at this speed only 75% of work will be completed, So he added 45 more workers to complete the work on time then find the initial numbers of workers.

90

45 days = Only 75% work is done

so in 15 days = \(\frac{75}{45}\) × 15 = 25% work is done

\(\frac{M_1d_1}{W_1}\) = \(\frac{M_2d_2}{W_2}\) ⇒ 

\(\frac{× × 15 }{25%}\)  =  \(\frac{(x + 45) × 30}{75%}\)

⇒ x × 15 = \(\frac{30 x + 45 × 30}{3}\)

          45 x - 30 x = 45 × 30

⇒ 15 x = 45 × 30 ⇒ x = 90