In the class of 24 students, half are doing silent reading, and a third are playing board games. The rest are catching up on homework. How many students are catching up on homework? Give the rationale and then the answer.
Let's think step by step. 24 / 2 = 12 students are doing silent reading. 24 / 3 = 8 students are playing board games. So 12 + 8 = 20 students are accounted for. Then 24 - 20 = 4 students are catching up on homework.. The answer is: 4.

Kim spends $25,000 to open a store. She makes $4000 a month in revenue and her expenses are $1500 a month. How long would it take to pay back the cost to open the store? Give the rationale and then the answer.
Let's think step by step. Her profit is 4000 - 1500 = $2500. So it takes 25000 / 2500 = 10 months to make back the money.. The answer is: 10.

Eugene built a model house out of toothpicks and a deck of playing cards. For every card, he used 75 toothpicks. The deck of playing cards had 52 cards, and Eugene used all but 16 of the cards to build his house. If a box of toothpicks contains 450 toothpicks, how many boxes of toothpicks did Eugene use to create his model house? Give the rationale and then the answer.
Let's think step by step. If Eugene used all but 16 of the 52 cards, then he used 52 - 16 = 36 cards. If for every card he used 75 toothpicks, then a box of toothpicks would have enough toothpicks for 450 / 75 = 6 cards. Since one box has enough toothpicks for 6 cards, then for 36 cards he would need 36 / 6 = 6 boxes of toothpicks.. The answer is: 6.