On Thursday 15 * 3 = 45 books were sold. On Friday 45 / 5 = 9 books were sold. Adding up all three days 15 + 45 + 9 = 69 books were sold by Friday.
The answer: 69
Reverse engineering the question: A new book sold 15 copies at the bookstore on Wednesday. On Thursday the book sold three times that many copies. On Friday the book sold one-fifth the number of copies it did on Thursday. How many copies of the book did the bookstore sell by Friday?
Reasoning and answer: Since Cristian's house has ten rooms, he painted 3 / 5 * 10 = 6 rooms with green color. The number of rooms he painted with purple is 10 - 6 = 4 rooms. Since each room in the house has eight walls, the number of walls painted purple is 8 * 4 = 32.
The answer: 32
What was the question?
Question: Johan has a ten-bedroom house with 8 walls in each room. He paints 3/5 of the rooms in the house green and paints the rest of the rooms with purple color. How many walls in the house did he paint purple?
Anya has 4 x 4 = 16 erasers. Thus, Anya has 16 - 4 = 12 more erasers than Andrea.
The answer: 12
Reverse engineering the question: Anya has 4 times as many erasers as Andrea. If Andrea has 4 erasers, how many more erasers does Anya have than Andrea?
Reasoning and answer: At first Jeff paid, $300 / month x 12 months = $3,600 / year. He paid $3,600 / year x 3 years = $10,800 the firsts 3 years. The final 2 years he paid $350 / month x 12 months = $4,200 / year. He paid $4,200 / year x 2 years = $8,400 the last 2 years. He paid the owner $10,800 + $8,400 = $19,200 in total.
The answer: 19200
What was the question?
Question: Jeff wanted to rent an apartment to live in for the next 5 years until he finishes his studies. He found a nice apartment next to his school, the owner asks Jeff to pay $300 each month, Jeff agreed, and for the first 3 years everything went fine, but then the owner wanted to raise the price for each month to $350. Jeff agreed again and continued paying until he graduated. How much did Jeff end up paying for the apartment throughout the 5 years?
First find the number of green straws each mat needs: 30 orange straws / 2 orange straws / green straw = 15 green straws. Then find the total number of straws in each mat: 15 straws + 20 straws + 30 straws = 65 straws. Then multiply that number by the number of mats to find the total number of straws Ginger needs: 65 straws / mat * 10 mats = 650 straws.
The answer: 650
Reverse engineering the question: Ginger is weaving mats out of colored straw. Each mat takes 20 red straws, 30 orange straws, and half as many green straws as orange straws. How many straws does she need to make 10 mats?
The volume of the box is 8 x 10 x 12 = 960 cu in. The volume of a wooden block is 3 x 2 x 4 = 24 cu in. 960 / 24 = 40 wooden blocks can fit into the box.
The answer: 40
Reverse engineering the question:
A box is 8 inches in height, 10 inches in width, and 12 inches in length. A wooden building block is 3 inches in height, 2 inches in width, and 4 inches in length. How many building blocks can fit into the box?