The average age of a group of some persons is 18.75 years. By joining 30 new persons with an average age of 14.25 years, the average age of the group becomes 15 years. Find out the number of people in the group initially? round off the number to nearest whole number
Answers
Explanation:
In a group of ten people, the average age is 18. When two people leave the group, the average age drops to 10. One of the two persons that left is 80 years old, how old is the other one?
The other one is 20 years old.
In the original group of people, there are ten people and the average age is 18. To work out the total age (every age added together) of this group, simply do 18*10, which equals 180.
Now in the new group, two people have left, so there are 8 people in the group and their average age is 10. The total age of this group is 8*10, which is 80.
So the original group has a total age of 180, and the new one has a total age of 80, meaning that there is a difference of 100 between the groups. One of the people that leaves is 80 years old, meaning that for the difference to be 100 between the two groups, the other person that leaves has to be 20 years old, since 80+20=100.