\tN workmen could have build a dam in 50 days. 80 of them did not turn up. find N, if the work took 70 days for completion.(A) 340(B) 320(C) 350(D)280

Dear Student,

N men 50 days
Toatl work 50*N
N-80 men 70 days
Total work (N-80)*70

But in both cases work is finished
Hence
50*N= (N-80)*70
On solving N=280\

D is the correct choice