# Exponential functions

• May 10th 2012, 03:50 PM
victorwen28
Exponential functions
Hailey has begun a fitness program. The first week she ran 1 mile every day. Each week she increases the amount that she runs each day by 20%. In week 10, how many miles does she run each day? Give your answer to the nearest mile.

My solution:
A=P(1+r)^n
=1(1.2)^9
=5
• May 10th 2012, 04:30 PM
HallsofIvy
Re: Exponential functions
Yes, that is correct. "To the nearest mile" isn't all that accurate but if that was what you were told to do ....
• May 10th 2012, 04:33 PM
victorwen28
Re: Exponential functions
How come the answer key to the amsco textbook says it is 6 miles?
• May 10th 2012, 05:03 PM
skeeter
Re: Exponential functions
Quote:

Originally Posted by victorwen28
How come the answer key to the amsco textbook says it is 6 miles?

because the individual who made the answer key erroneously calculated $1.2^{10}$ , which is the number of miles run each day in week 11.
• May 10th 2012, 05:06 PM
victorwen28
Re: Exponential functions
So it is a guaranteed 5 miles?