There are 80 / 100 * 2300 = 1840 books in English at the library. Out of these books, only 60 / 100 * 1840 = 1104 were published inside the country. So there are 1840 - 1104 = 736 books in English published outside of the country.
The answer: 736
Reverse engineering the question: In the school's library, there are 2300 different books. 80% of all the books are in English, but only 60% of these books were published in the country. How many English-language books have been published outside the country?


Reasoning and answer: The tree has been planted for 9 - 4 = 5 years. It will take another 7 - 5 = 2 years for it to bear fruit. Lydia will be 9 + 2 = 11 years old.
The answer: 11
What was the question?
Question: It takes 7 years for an apple tree to bear fruit. If Lydia planted a tree when she was 4 years old and is now 9 years old, how old would she be when she gets to eat an apple from her tree for the first time?


Jar B has 28 + 12 = 40 marbles. Jar C has 2 x 40 = 80 marbles. Therefore, there are 28 + 40 + 80 = 148 marbles altogether.
The answer: 148
Reverse engineering the question: Jar A has 28 marbles. Jar B has 12 more marbles than jar A. Jar C has twice as many marbles as jar B. How many marbles are there altogether?


Reasoning and answer: Each minute last 60 seconds, so that means for the fries to be fully cooked Bill needs to cook them for 5 * 60 = 300 seconds. Since Bill had the fries in the oven for 45 seconds so far, that means they need to stay in the oven for another 300 - 45 = 255 seconds.
The answer: 255
What was the question?
Question: Bill put his french fries in the oven after it finished heating. The recommended time was 5 minutes for them to be fully cooked. He put them in for 45 seconds. How many seconds remained?


First subtract the cost of Mark's groceries from the amount he gives the cashier to find how much he gets in change: $7.00 - $4.20 - $2.05 = $0.75. Then subtract the value of a quarter in cents (25) and the value of a dime in cents (10) from the change amount to find how much Mark gets paid in nickels: $0.75 - $0.25 - $0.10 = $0.40. Now divide the amount Mark gets in nickels by the value per nickel in cents (5) to find how many nickels Mark gets: $0.40 / $0.05 / nickel = 8 nickels.
The answer: 8
Reverse engineering the question: Mark buys a loaf of bread for $4.20 and some cheese for $2.05. He gives the cashier $7.00. If the cashier only has 1 quarter and 1 dime in his till, plus a bunch of nickels, how many nickels does Mark get in his change?


If there were 26 pink hard hats and Carl took away 4 pink hard hats, the number of pink hard hats that remained is 26 - 4 = 22. John also took away 6 pink hard hats, leaving 22 - 6 = 16 pink hard hats in the truck. If John also took twice as many green hard hats as pink hard hats, he took 2 * 6 = 12 green hard hats. The total number of green hard hats that remained in the truck is 15 - 12 = 3. In the truck, after some are taken, there were 3 green hard hats + 16 pink hard hats = 19 hard hats in the truck. Altogether, 19 green and pink hard hats + 24 yellow hards hats = 43 hard hats remained in the truck.
The answer: 43
Reverse engineering the question:
In a truck, there are 26 pink hard hats, 15 green hard hats, and 24 yellow hard hats. If Carl takes away 4 pink hard hats, and John takes away 6 pink hard hats and twice as many green hard hats as the number of pink hard hats that he removed, then calculate the total number of hard hats that remained in the truck.