5 people were asked about the time in a week they spend in doing social work in their community. They said 10, 7, 13, 20 and 15 hours, respectively. Find the mean (or average) time in a week devoted by them for social work.

5 people of a locality were asked about the time they spent in a week in doing social work. They told the number of hous as: x,x+3,x+6,x+7,x+4. find the mean number of devoted by first three members. If mean number of hours of 5 persons is 11 hours, what values do we draw from above data?

10 men can do 2/5 part of a work in 10 days. Find time taken by 25 men to complete the whole work.

If 5 men can do a work in 2 days and 3 boys can do the same work in 5 days, then find the time taken to complete same work by 10 men and 3 boys.