Question

For a parking meter, one quarter earns 30 minutes of parking time. One dime equals 15 minutes of parking time. One nickel earns 7 minutes. What is the minimum number of coins it would take to park 1 hour 20 minutes?

Answer 1

3 (quarters)

Explanation:

One could pay for exactly 80 minutes (1 h, 20 min) of parking using 5 nickels (35 min), 1 dime (15 min), and 1 quarter (30 min), for a total of 7 coins.

On the other hand, one could pay for 90 minutes (1 h, 30 min) using 3 quarters.

The minimum number of coins required to purchase 80 minutes of parking time is 3 (quarters).