20 of 50 marbles are white so there are 50 - 20 = 30 red and blue marbles. The number of red marbles and blue marbles is the same, so there are 30 / 2 = 15 of each color. The difference between the number of white marbles and blue marbles is 20 - 15 = 5. Double the difference is 5 * 2 = 10 marbles. 10 marbles are removed to leave 50 - 10 = 40 marbles.
The answer: 40
Reverse engineering the question: There are 50 marbles in a box which has a mixture of white, red and blue marbles. There were originally 20 white marbles and an equal number of red and blue marbles. Jack removes a number of marbles equal to double the difference between the number of white marbles and the number of blue marbles. How many marbles are left in the box?


Reasoning and answer: In total Liam has saved ($500 / month * 12 months / year) * 2 years = $12,000. When Liam pays his bills, he will have $12,000 - $3,500 = $8,500 left.
The answer: 8500
What was the question?
Question: Liam wants to go to Paris, but first, he has to pay his bills. His trip costs $7,000, and his bills cost $3,500. Knowing that Liam has saved $500/month for 2 years, how much money will he have left after paying his bills?


He ate 2 * 1 = 2 pounds of broccoli. There are 51 / 3 = 17 calories in each pound of broccoli. So he ate 2 * 17 = 34 calories of broccoli. He ate 1 * 51 = 51 calories of carrots. So in total he ate 51 + 34 = 85 calories.
The answer: 85
Reverse engineering the question: Tom eats a pound of carrots and twice as much broccoli. If carrots have 51 calories per pound and broccoli has 1/3 that many calories, how many calories did he eat in total?


Reasoning and answer: Reginald counted two fewer shooting stars than did Bridget, or a total of 14 - 2 = 12 shooting stars. Sam counted 4 more shooting stars than did Reginald, or a total of 12 + 4 = 16 shooting stars. The average number of shooting stars observed for the three of them was (14 + 12 + 16) / 3 = 14 shooting stars. Thus, Sam counted 16 - 14 = 2 more shooting stars than was the average number of shooting stars observed for the three of them.
The answer: 2
What was the question?
Question: Bridget counted 14 shooting stars in the night sky. Reginald counted two fewer shooting stars than did Bridget, but Sam counted four more shooting stars than did Reginald. How many more shooting stars did Sam count in the night sky than was the average number of shooting stars observed for the three of them?


Carla is currently 30 - 6 = 24 years old. Louis is 55 - 24 = 31 years old at present.
The answer: 31
Reverse engineering the question: In 6 years, Carla will be 30 years old. The sum of the current ages of Carla and Louis is 55. How old is Louis now?


The second dog eats 1.5 x 2 = 3 cups of dog food. The third dog eats 3 + 2.5 = 5.5 cups. So, Hannah should prepare 1.5 + 3 + 5.5 = 10 cups.
The answer: 10
Reverse engineering the question:
Hannah has three dogs. The first dog eats 1.5 cups of dog food a day. The second dog eats twice as much while the third dog eats 2.5 cups more than the second dog. How many cups of dog food should Hannah prepare in a day for her three dogs?