Q: Hilary is collecting her toenails in a jar to gross out her sister. She can fit 100 toenails in the jar, unless they are from her two big toes, which are twice as big as the rest. She has already filled it with 20 big toenails and 40 regular toenails. How many regular toenails can she fit into the remainder of the jar?
A: The 20 big toenails take up as much space as 40 regular toenails because 20 x 2 = 40. She has filled up 80 toenails worth because 40 + 40 = 80. She can fit 20 regular toenails in the jar because 100 - 80 = 20. The answer is 20.

Q: John can read a book 60% faster than his brother. If his brother takes 8 hours to read a book, how long would it take John to read 3 books?
A: Reading 60% faster means John's brother takes 1 + .6 = 1.6 times as long as John to read. So John reads a book in 8 / 1.6 = 5 hours. So it would take John 5 * 3 = 15 hours to read 3 books. The answer is 15.

Q: The number of short students in a class is 2/5 of the total number of students. If there are 90 tall students, and the class has 400 students, calculate the total number of students with average height.
A:
The number of short students in the class is 2 / 5 * 400 = 160. The total number of short and tall students is 160 + 90 = 250. Since there are 400 students in the class, the number of students with average height is 400 - 250 = 150. The answer is 150.