Brittney can chop 15 / 5 = 3 onions in one minute. Carl can chop 20 / 5 = 4 onions in one minute. Brittney can chop 3 x 30 = 90 onions in 30 minutes. Carl can chop 4 x 30 = 120 onions in 30 minutes. Carl can chop 120 - 90 = 30 more onions than Brittney in 30 minutes.
The answer: 30
Reverse engineering the question: Brittney can chop 15 onions in 5 minutes. Carl can chop 20 onions within that same time. How many more onions can Carl chop in 30 minutes than Brittney?


Reasoning and answer: Max finished history in 20 * 2 = 40 minutes. Finishing geography took the most time, which is 40 * 3 = 120 minutes. In total, for all three subjects, Max needed 20 + 40 + 120 = 180 minutes.
The answer: 180
What was the question?
Question: Max was doing homework in three different subjects. It took him 20 minutes to finish tasks from biology and two times more time to finish history. Geography took him the most time, three times more than history. How much time did Max spend on doing his homework?


1 bottle of soap will last for 4 washes and he needs enough bottles for 20 weeks so 20 / 4 = 5 bottles. Each bottle cost $4.00 and he needs 5 bottles so he will spend $4 * 5 = $20.00 on car soap.
The answer: 20
Reverse engineering the question: Jake can wash his car with 1 bottle of car wash soap 4 times. If each bottle costs $4.00, and he washes his car once a week for 20 weeks, how much does he spend on car soap?


Reasoning and answer: There have been 450 puzzles because 15 x 30 = 450. It would take 1,350 minutes to find all the Waldo's because 450 x 3 = 1,350.
The answer: 1350
What was the question?
Question: There have been 15 "Where's Waldo?" books published. Each book has 30 puzzles to find Waldo. The average person takes 3 minutes to find Waldo in a puzzle. How long would it take to find every Waldo?


40 / 4 = 10 kids went tubing. 10 / 2 = 5 kids went rafting and tubing.
The answer: 5
Reverse engineering the question: There were 40 kids on Lake Pleasant. A fourth of the kids went tubing, but only half of the tubers went rafting. How many of the kids who joined the rafting excursion were also on the tubing excursion?


He spent 2 * 2 = 4 years learning to climb. He spends 5 * 7 = 35 months climbing all 7 mountains. After a 13 month break, he starts diving so that is 35 + 13 = 48 months. That means it is 48 / 12 = 4 years. So in total it all took 2 + 4 + 4 + 2 = 12 years.
The answer: 12
Reverse engineering the question:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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A man decides to try and do everything off his bucket list while he is still young and fit enough to finish it all. One of his goals was to climb the seven summits. He realizes first he has to get in shape to do it and it takes him 2 years of working out to get healthy enough to take up mountain climbing. He then spends twice that long learning how to be a technically proficient mountain climber. After that he starts with the simplest mountain on the list and climbs them all. He spends 5 months climbing each mountain. After that he takes 13 months learning to dive and dives through all the caves he wants in 2 years. How much time did it take to get through all these goals?