Total period = 10 days
But work completed in = 12 days
No. of men were absent = 5
Let the number of men in the beginning = x
Now x men can do a piece work in = 10 days
1 man will do it in = 10x x days
And (x – 5) will do it in = (10 × x)/(x – 5) days
∴ 10x/(x – 5) = 12 ⇒ 10x = 12x – 60
⇒ 12x – 10x = 60 ⇒ 2x = 60
⇒ x = 60/2 = 30
∴ No. of men in the beginning = 30