Orville’s speedboat will run 4 hours at full throttle or 7 hours at half throttle. We went out to East Sister Island at full throttle. It took one hour. We returned at half throttle. It took 3 hours. Then we refilled the fuel tank. It took 3.8 gallons of diesel fuel to refill the tank. How much fuel does the tank hold?
We assume we started with a full tank of fuel. On the way out, we used 1/4 tank. On the way back, 3/7 tank. We used a total of 3.8 gallons of fuel.
| So | 1 | t + | 3 | t = 3.8 → | 7t + 12t | = 3.8 → 19t = 28 x 3.8 = 106.4 → t = 5.6 gallons. |
| 4 | 7 | 28 |