2011 AMC 12A Problems/Problem 1

Solution

The base price of Michelle's cell phone plan is <dollar/>20. If she sent 100 text messages and it costs 5 cents per text, then she must have spent 500 cents for texting, or <dollar/>5. She talked for 30.5 hours, but 30.5-30 will give us the amount of time that she has to pay an additional amount for. 30.5-30=.5 hours=30 minutes. Since the price for phone calls is 10 cents per minute, the additional amount Michelle has to pay for phone calls is 30*10=300 cents, or <dollar/>3. Adding <dollar/>20+<dollar/>5+<dollar/>3=<dollar/>28=.