There are 300 x 2 / 3 = 200 females in the school. So, 300 - 200 = 100 are males. Out of the 100 males, 100 x 1 / 10 = 10 are male foreign students. Thus, there are 100 - 10 = 90 non - foreign male students.
The answer: 90
Reverse engineering the question: At a certain school, 2/3 of the population are females. One-tenth of the males are foreign students. If the school has 300 students, how many students are non-foreign male students?


Reasoning and answer: Originally, there were 90 * 2 / 3 = 60 in the cafeteria. Originally, there were 90 - 60 = 30 outside the cafeteria. Then 30 * 1 / 3 = 10 ran inside. The number of students inside the cafeteria grew by 10 - 3 = 7. There are now 60 + 7 = 67 students in the cafeteria.
The answer: 67
What was the question?
Question: There are 90 students who have lunch during period 5. Today, two-thirds of the students sat in the cafeteria, while the remainder sat at the covered picnic tables outside. But some yellow-jackets were attracted to their food, and so one-third of the students outside jumped up and ran inside to the cafeteria, while 3 of the students in the cafeteria went outside to see what all the fuss was about. How many students are now in the cafeteria?


First find the number of tadpoles Trent released: 180 tadpoles * .75 = 135 tadpoles. Then subtract the number he let go from the total number to find the number of tadpoles he keeps: 180 tadpoles - 135 tadpoles = 45 tadpoles.
The answer: 45
Reverse engineering the question: Trent caught 180 tadpoles then let 75% of them go. How many did he keep?


Reasoning and answer: Since each chapter of the book has 40 pages, Mitchell had read 10 * 40 = 400 pages from the first ten chapters. After reading 20 pages of the eleventh chapter, the total number of pages that Mitchell had read is 400 + 20 = 420. The next two chapters that she read had 2 * 40 = 80 pages. In total, Mitchell read 420 + 80 = 500 pages of the book that day.
The answer: 500
What was the question?
Question: Studying for her test, Mitchell had read ten chapters of a book before 4 o'clock. When it clocked 4, Mitchell had read 20 pages of the 11th chapter of the book she was studying from. After 4 o'clock, she didn't read the remaining pages of chapter eleven but proceeded and read 2 more chapters of the book. If each chapter in the book had 40 pages, calculate the total number of pages that Mitchell had read altogether?


The total number of hours Sandy worked on Friday, Saturday and Sunday was 10 + 6 + 14 = 30 hours. Beth made 30 × $15 = $450 in those 3 days.
The answer: 450
Reverse engineering the question: Sandy earns $15 per hour. She worked 10 hours on Friday with her best friend, 6 hours on Saturday alone and 14 hours on Sunday with her other co-workers. How much money did Sandy earn in all on Friday, Saturday and Sunday?


The first movie was 2 * 60 = 120 minutes. So this movie is 120 * .6 = 72 minutes longer. So this movie is 192 minutes. It also cost 50 * 2 = $100 per minute to film. So it cost 192 * 100 = $1920.
The answer: 1920
Reverse engineering the question:
Janet filmed a new movie that is 60% longer than her previous 2-hour long movie. Her previous movie cost $50 per minute to film, and the newest movie cost twice as much per minute to film as the previous movie. What was the total amount of money required to film Janet's entire newest film?