Answer:
24.25 years
Explanation:
We know that average of a set = (sum of all terms) / (number of terms). Right now, we know two things: the average of the set (21 years) and the number of terms in the set (5). Therefore, we can rewrite the equation to solve for the sum of all terms.
We have: 21 =
sum = 21 · 5 = 105
Now we know the sum of ages of the 5 girls. We want to find the average age of the 4 remaining girls when we take out the girl who is 8 years old. As previously stated, to find the average of a set, we need to know two things: the sum of all terms in the set and the number of terms in the set. Right now, we only know one of those things: the number of terms in the set, which is 4. To find the sum, we can simply subtract the 8-year-old girl's age from the sum of ages of the 5 girls, which would be 105 - 8 = 97.
Therefore, the average age of the 4 remaining girls is
years.
Hope this helps!