Question: A train takes 4 hours to reach a destination at a speed of 50 miles per hour. How long would it take if it traveled at 100 miles per hour instead?
Answer with step-by-step thinking: The distance to the destination is 4 hours * 50 miles / hour = 200 miles. Traveling at 100 miles per hour, it will take 200 miles / (100 miles / hour) = 2 hours.
So the answer is 2.

Question: At its current growth rate, a certain plant will be 80 feet tall after a year. If the plant grows at the same rate every month and is currently 20 feet tall, what's its monthly growth rate in feet?
Answer with step-by-step thinking: If the plant is currently 20 feet tall, it will have grown by 80 - 20 = 60 feet after a year. Since a year has 12 months, and the tree grows at the same rate every month, the tree grows at 60 / 12 = 5 feet every month.
So the answer is 5.

Question: Derek is watching the construction cranes downtown and is trying to figure out how much taller they have to be than the building they are building. He sees one crane that is 228 feet tall finishing a building that was 200 feet tall. He sees another that is 120 feet tall finishing a building that is 100 feet tall. The final crane he sees is 147 feet tall, finishing a building that is 140 feet tall. On average, what percentage taller are the cranes than the building?
Answer with step-by-step thinking:
The first crane is 14 percent taller because if 200 + 200x = 228 then x = .14. The second crane is 20 percent taller because if 100 + 100x = 120 then x = .2. The third crane is 5 percent taller because if 140 + 140x = 147 then x = .5. The total percent is 39 because 14 + 20 + 5 = 39. The average percent greater the height of the crane is than the building is 13 because 39 / 3 = 13.
So the answer is 13.