A group of workers can complete a piece of work in 15 days, when they are working individually. On the first day one man works, on the second day another man joins him, on the third day one more man joins them and the process continues until the whole work is completed. Then find out how many days will be required to complete the work?

5 days

Let A man complete 1 piece of work in a day then total work = 15 units

As per question, Work done by:

1 man in 1st day = 1 unit

2 men in 2nd day = 2 units

3 men in 3rd day = 3 units

Let the whole work will be completed in n days

Then,

⇒ 1 + 2 + 3 ............n = 15 units

⇒ \(\frac{n × (n+1)}{2}\) = 15 units

⇒ n × (n+1) = 30

⇒ n = 5 days