After visiting my Great Aunt Bernie, I travelled home in my old jalopy. The car was so old and battered that I was stuck in the second gear. This meant that I could only travel along at a steady 30 miles per hour and managed a paltry 20 miles per gallon of petrol. At the start of the journey I had placed exactly 10 gallons of petrol into the tank. I knew that the petrol tank had a leak and lost petrol at the rate of half a gallon per hour. As I arrived home, the car stopped because it had run out of petrol and I only just made it. How far was it from my Great Aunt’s to my home?
Answer
150 miles; as I was travelling at 30 mph, I was using 1.5 gallons of petrol and losing 0.5 gallon of petrol for each hour I travelled. Therefore, I was getting through the petrol at a total rate 2 gallons per hour. Since I had 10 gallons of petrol at the start, I could travel for 5 hours before running out. 5 hours at 30 mph is 150 miles.
