[Question]Du Chin bakes 200 meat pies in a day. He sells them for $20 each and uses 3/5 of the sales to buy ingredients to make meat pies for sale on the next day. How much money does Du Chin remain with after setting aside the money for buying ingredients?
[Answer]From the 200 meat pies, Du Chin makes 200 * $20 = $4000 after the sales. The amount of money he uses to buy ingredients to make pies for sale on the next day is 3 / 5 * $4000 = $2400. After setting aside money for buying ingredients, Du Chin remains with $4000 - $2400 = $1600. The answer is 1600.

[Question]Luisa drives 10 miles to the grocery store, 6 miles to the mall, 5 miles to the pet store, then 9 miles back home. One gallon of gas can be used to drive 15 miles. If one gallon of gas costs $3.50, what is the total cost of the gas for Luisa's entire trip?
[Answer]Luisa drives a total of 10 + 6 + 5 + 9 = 30 miles. Luisa uses 30 / 15 = 2 gallons of gas for her trip. The total cost of the gas for Luisa's trip is 2 * $3.50 = $7. The answer is 7.

[Question]Lola and Dora combined their allowance of $9 each to buy a deck of playing cards for $10, they also bought $2 boxes of stickers and split the boxes evenly. How many packs of stickers did Dora get?
[Answer]Lola and Dora together have $9 / person x 2 people = $18. After buying the deck of cards they had $18 - $10 = $8. With 8 dollars they bought $8 / $2 / pack = 4 packs of stickers. Dora received 4 packs / 2 people = 2 packs of stickers. The answer is 2.

[Question]There are three times as many girls as boys in the Biology class. The Physics class has 200 students. If the Biology class has half as many students as the Physics class, how many boys are in the Biology class?
[Answer]
The Biology class has 200 / 2 = 100 students. The boys in the Biology class are 1 / 4 * 100 = 25 students. The answer is 25.