After the accident, Mike can only type 65 words / minute - 20 words / minute = 45 words / minute. So, he will be able to finish typing the document in 810 words / 45 words / minute = 18 minutes.
The answer: 18
Reverse engineering the question: Mike can type 65 words per minute. Due to a minor accident, Mike cannot use his right hand for a while so that his typing speed is now 20 words less per minute. If he is supposed to type a document with 810 words, how many minutes will it take him to finish typing the document?


Reasoning and answer: Six sets of 1 dozen of doughnuts cost $8 x 6 = $48. Three sets of 2 dozens of doughnuts cost $14 x 3 = $42. Therefore, you can save $48 - $42 = $6.
The answer: 6
What was the question?
Question: If you buy a dozen of doughnuts, it costs $8; but if you buy 2 dozens, it costs $14. How much will you save from buying 3 sets of 2 dozens than buying 6 sets of 1 dozen?


Let x be the number of animals in the Rain Forest exhibit. 3x - 5 = 16. 3x = 21. x = 7.
The answer: 7
Reverse engineering the question: The Reptile House at the zoo has 5 fewer animals than 3 times the number of animals housed in the Rain Forest exhibit. If the Reptile House has 16 animals, how many are in the Rain Forest exhibit?


Reasoning and answer: Store A has a $125 x 8 / 100 = $10 discount. So the smartphone from store A will only cost $125 - $10 = $115. Store B has a $130 x 10 / 100 = $13 discount. So the smartphone from store B will only cost $130 - $13 = $117. Thus, store A's smartphone is $117 - $115 = $2 cheaper than that of store B.
The answer: 2
What was the question?
Question: Two stores sell the same model of smartphone, but they offer it at different prices and with different discounts. Store A lists the smartphone at a full price of $125 and offers an additional discount of 8%. Store B lists the same smartphone for $130 and offers an additional discount of 10%. After both stores' discounts are applied, how much cheaper is store A's smartphone than store B's smartphone?


Rachel's age is 8 x 2 = 16. Collete's age is 8 / 2 = 4. Therefore the difference between their age is 16 - 4 = 12.
The answer: 12
Reverse engineering the question: Rachel is twice as old as Rona and Collete's age is half the age of Rona's. If Rona is 8 years old, what is the difference between the age of Collete and Rachel?


Bush is younger than Matt by 3 years, so if Bush is 12 years old then Matt is 12 + 3 = 15 years old. In 10 years' time, Matt will be 10 + 15 = 25 years old.
The answer: 25
Reverse engineering the question:
Bush and Matt are brothers. Bush is younger than Matt by 3 years. This year Bush will be 12 years old. What will be Matt's age 10 years from now?