the ages of six girls are as follows; 17,8,12,15,15,13. what would be the age of the seventh girl that would make the mean age of all the girls to be 13 years

11 yrs

Step-by-step explanation:

Mean = sum of ages/number of ages

Let the age of the seventh girl be A

Given the addition of the age of the seventh girl will make the mean of the ages be 13,

So,

13 = 17+8+12+15+15+13+A/7

Add up the ages

13 = 80 + A / 7

Cross multiply

80 + A = 13 x 7

80 + A = 91

Subtract 80 from both sides to isolate A

80 - 80 + A = 91 - 80

A = 11

The age of the seventh girl is 11