Answer:
56 years
Step-by-step explanation:
we know that
1) The average of group of 13 boys is 13 years
so
Remember that
The average is the sum of the ages divided by the number of boys
The sum of the ages is equal to the average multiplied by the number of boys
The number of boys is 13
The average is 13
The sum of the ages is ----> 13*13=169
2) When two more boys joined the group, the average age rose by 2 years
so
Now the number of boys is 13+2=15
The average is 13+2=15
The sum of the ages is -----> 15*15=225
To find out the sum of ages of two new boys, subtract the original sum of the ages from the new sum of the ages
225-169=56 years
