The percentage of adult height attained by a girl who is x years old can be modeled by f(x) = 62 +35 log(x-4), where x represents the girl’s age (from 5 to 15) and f(x) represents the percentage of her adult height. Use the formula to solve the following.

Approximately what percentage of her adult height has a girl attained at age 13?

Solution:

When x=13, f(13) = 62 +35 log(13-4)= 95.40

So 95.40% of her adult height has a girl attained at age 13