Answer:
even I think
Step-by-step explanation:
Answer:
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