Question

15 men could finish a piece of work in 210 days. But at the end of 100 days, 15 additional men are employed. In how many more days will the work be complete? A.

Answer 1

Therefore,
1 man requires 15 * 210 = 3150 days to complete the same work 
So, in 1 day 1 man complete 1/3150 of the total work 
Thus,
In 100 days 15 men completes (15 * 1/3150 * 100) = 10/21 of the total work 
After 100 days there are 30 men,
They will complete the remaining task i.e. 1 - 10/21 of the total work in 1/30 * 11/21 * 3150 = 55 days.

Answer 2

Step-by-step explanation:

10 day's work by 15 men = 10/210 = 1/21

At the end of every 10 days 15 additional men are employed i.e., for the next 10 days we have 15 + 15 = 30 men

∴ Next 10 day's work by 30 men = 2/21

Hence in 20 days only (1/21 + 2/21) = 3/21 work is completed

To complete the whole work we have to reach the value of (21/21) work.

Now, (1/21) + (2/21) + (3/21) + ......... (6/21) = 21/21 = 1

Hence total time to complete the whole wok 10 + 10 + 10 + 10 + 10 + 10 = 60 days

hope it helps you....