Aircraft burns 2100lbs per half hour and can hold 8400lbs in its tank. How many times must it refuel in a 13hr trip? My answer is 7 times.
I think the correct answer is 6 because they ask how many times the aircraft must REfuel. So, the first full tank doesn't count.
2100 lbs per 30 minutes means 4200 lbs per hour. If the tank holds 8400 lbs then a tank lasts 2 hours, which means that:
The aircraft leaves with the tank full. This doesn't count.
1. 2 hours later, it refuels (total trip time: 2 hours).
2. 2 hours later, it refuels (total trip time: 4 hours).
3. 2 hours later, it refuels (total trip time: 6 hours).
4. 2 hours later, it refuels (total trip time: 8 hours).
5. 2 hours later, it refuels (total trip time: 10 hours).
6. 2 hours later, it refuels (total trip time: 12 hours).
1 hour later it will reach its destination and it will still have 4200 lbs left in the tank (enough for 1 more hour). So the final answer is 6 times.
I think this question is aimed at testing how focused you are, because it is more of an English comprehension question rather than a math one.
I hope this helps!