Archie is playing with his marbles outside. He loses 60% of them into the street. Of the remaining ones, he loses half down a sewer. If he has 20 left, how many did he start with? Give the rationale and then the answer.
Let's think step by step. He had 40 before losing them into the sewer because 20 x 2 = 40. He started with 100 because 40 / .4 = 100.. The answer is: 100.

A school has 15 classrooms. One-third of these classrooms have 30 desks in each classroom and the rest have 25 desks in each classroom. Only one student can sit at one desk. How many students can this school accommodate so that everyone has their own desk? Give the rationale and then the answer.
Let's think step by step. One - third of the classrooms have 30 desks, so there are 1 / 3 * 15 = 5 classrooms like that. The rest, which means 15 - 5 = 10 classrooms, have 25 desks. One - third of the classrooms can fit 5 * 30 = 150 students. The rest can fit 10 * 25 = 250 students. So in total, the school can be filled with 150 + 250 = 400 students.. The answer is: 400.

To make pizza, together with other ingredients, Kimber needs 10 cups of water, 16 cups of flour, and 1/2 times as many teaspoons of salt as the number of cups of flour. Calculate the combined total number of cups of water, flour, and teaspoons of salt that she needs to make the pizza. Give the rationale and then the answer.
Let's think step by step. To make the pizza, Kimber half as many teaspoons of salt as the number of cups of flour, meaning she needs 1 / 2 * 16 = 8 teaspoons of salt. The total number of cups of flour and teaspoons of salt she needs is 8 + 16 = 24. She also needs 10 cups of water, which means the total number of cups of water and flour and teaspoons of salt she needs is 24 + 10 = 34.. The answer is: 34.