Question: Christina and her friend are driving across the state. When Christina is driving the speed limit is 30 miles per hour. When her friend is driving, the speed limit is 40 miles per hour. The drive is 210 miles total. If her friend drives for 3 hours and both drive at the speed limit, how many minutes will Christina drive? Think carefully first, then make a decision:
The friend drives 40 * 3 = 120 miles. Thus, Christina drives 210 - 120 = 90 miles. Since the speed limit is 30 miles per hour when Christina is driving, she drives for 90 / 30 = 3 hours. Thus, she drives for 3 * 60 = 180 minutes. So the answer is 180.