15.5 + (2 * 21.5) = 58.5 km. 74.5 - 58.5 = 16 kilometers. The last part of the race is 16 kilometers.
The answer: 16
Reverse engineering the question: Silvio was running a race that had 4 parts. The total length of the race was 74.5 kilometers. The first part of the race is 15.5 kilometers long. The second and third parts are each 21.5 kilometers long. How many kilometers is the last part of the race?


Reasoning and answer: Twice the number of Aaron's brothers is 6 + 2 = 8. Aaron has 8 / 2 = 4 brothers.
The answer: 4
What was the question?
Question: Aaron has some brothers. Bennett has 6 brothers. If the number of Bennett's brothers is two less than twice the number of Aaron's brothers, what is the number of Aaron's brothers?


The number of birthday presents that David found is 60 / 2 = 30. For his birthday and Christmas, David found a total of 30 + 60 = 90 presents.
The answer: 90
Reverse engineering the question: The number of Christmas presents David found was twice as many as the number of birthday presents. If David found a total of 60 Christmas presents, how many presents did he get all together?


Reasoning and answer: He increases his sleep by 6 / 3 = 2 hour per night. So he now gets 6 + 2 = 8 hours of sleep per night.
The answer: 8
What was the question?
Question: Tom has only been getting 6 hours of sleep a day. He increases that by 1/3. How many hours of sleep does he get per night?


He writes for 4 - 1 = 3 hours per day. That means he writes 3 * 5 = 15 pages per day. So it would take him 735 / 15 = 49 days. That means it will take 49 / 7 = 7 weeks.
The answer: 7
Reverse engineering the question: James writes from 1 PM to 4 PM every night. He can write 5 pages per hour. How many weeks will it take to finish his 735-page book?


There were 800 x 20 / 100 = 160 parents who agreed to the tuition fee increase. So, there were 800 - 160 = 640 parents who disagreed.
The answer: 640
Reverse engineering the question:
A survey conducted by the school showed that only 20% of the 800 parents agree to a tuition fee increase. How many parents disagree with the tuition fee increase?