40 men complete one-third of a work in 40 days. How many more men should be employed to finish the rest of the work in 50 more days?

Work done = 1/3
Remaining work = (1 - 1/3) = 2/3
Let the number of additional men be N. (Direct proportion)
More days, Less men (Indirect proportion)
Work 1/3 : 2/3
Days 50 : 40
∴ 1/3 x 50 x (40 + N) = 2/3 x 40 x 40
⇒ 5 x (40 + N) = 2 x 40 x 4
⇒ 200 + 5N = 320
⇒ 5N = 320 - 200 = 120
∴ N = 120/5 = 24
∴ Required number of men = 24