Each part is 30 / 6 = 5 meters long. Since Liam used 4 parts, then he used 5 x 4 = 20 meters of the ribbon. So, 30 - 20 = 10 meters of ribbon is not used.
The answer: 10
Reverse engineering the question: Isaac cut his 30 meters ribbon into 6 equal parts. He then used 4 parts of the ribbon. How many meters of ribbon are not used?


Reasoning and answer: Tom is currently two times older than Ann, which means he is 6 * 2 = 12 years old. In ten years Ann is going to be 6 + 10 = 16 years old. And Tom is going to be 12 + 10 = 22 years old. So the sum of their ages will be 16 + 22 = 38.
The answer: 38
What was the question?
Question: Ann is 6 years old. Her brother Tom is now two times older. What will be the sum of their ages 10 years later?


Before the purchase, Bert had 300 * 1 / 2 = 150 stamps. So after the purchase he has 300 + 150 = 450 stamps.
The answer: 450
Reverse engineering the question: Bert bought some unique stamps for his collection. Before the purchase, he had only half the stamps he bought. If he bought 300 stamps, how many stamps does Bert have in total after the purchase?


Reasoning and answer: He rented the helicopter for 2 * 3 = 6 hours. So he paid 6 * 75 = $450.
The answer: 450
What was the question?
Question: Tom rents a helicopter for 2 hours a day for 3 days. It cost $75 an hour to rent. How much did he pay?


Each plastic chair costs $55 / 5 = $11. Two chairs cost $11 x 2 = $22. A portable table costs $11 x 3 = $33. Manny has to pay a total of $22 + $33 = $55. Thus, Manny will be left with $100 - $55 = $45.
The answer: 45
Reverse engineering the question: Three plastic chairs cost as much as a portable table. Five plastic chairs cost $55. If Manny wants to buy one portable table and two chairs, how much will be left in his $100?


In the full decks, John has a total of 52 cards in a full deck of cards * 3 full decks of cards = 156 cards. A half - full deck of cards contains 52 cards in a full deck of cards / 2 = 26 cards. So from the half - full decks, John has a total of 26 cards * 3 half - full decks = 78 cards. This is a total of 156 cards from full decks + 78 cards from half - full decks = 234 cards. After throwing some in the trash, he now holds a total of 234 cards - 34 trashed cards = 200 cards.
The answer: 200
Reverse engineering the question:
John is holding a poker night with his friends and is getting the decks of cards ready before his friends show up. After losing so many cards from various decks, John thinks he needs to count exactly how many cards he has to make sure he has enough full decks for the night. Each deck of cards should hold 52 cards. He finds 3 half-full decks of cards and 3 full decks of cards. As he is arranging them, he realizes that the quality of a lot of the cards is quite poor and decides to throw 34 of the cards in the trash. How many cards does John now have?