A certain number of persons can complete a work in 54 days. If there were 15 persons less, it would take 18 days more for the work to be completed. Initially, the number of persons is:

60 56 50 72

60

Formula to be used here, \( { M}_{1 } \) x \( { D}_{1 } \)  = \( { M}_{2 } \) x \( { D}_{2 } \) where, M = No. of Men, D = No. of Days, ⇒ Putting values in the formula, ⇒ M x 54 = (M - 15) x 72 ⇒ M = 60.