[Question]In a school with 800 students, 5/8 of the students are girls. Seven-tenths of the girls and two-fifths of the boys are in the primary grades, while the rest are middle schoolers. How many middle schoolers are there?
[Answer]There are 800 x 5 / 8 = 500 girls. So, there are 800 - 500 = 300 boys. There are 500 x 7 / 10 = 350 girls that are in the primary grades. Hence, 500 - 350 = 150 girls are middle schoolers. There are 300 x 2 / 5 = 120 boys that are in the primary grades. Hence, 300 - 120 = 180 boy students are middle schoolers. Therefore, a total of 150 girls + 180 boys = 330 middle schoolers. The answer is 330.
Q: John plays at the arcade for 3 hours. He uses $.50 for every 6 minutes. How much money did he spend, in dollars?
A: He was at the arcade for 3 * 60 = 180 minutes. So he put coins in 180 / 6 = 30 times. That means he spent 30 * .5 = $15. The answer is 15.
Question: For every 100 additional people that board a spaceship, its speed is halved. If the speed of the spaceship with 200 people on board is 500km per hour, what is its speed in km/hr when there are 400 people on board?
Answer: For every addition of 100 people added the speed is halved so for the first 100 people added its speed is 1 / 2 * 500 km / hr = 250 km / hr. For another addition of 100 people its speed is also halved, 1 / 2 * 250 km / hr = 125 km / hr. So for the total of 200 additional people, its speed is 125 km / hr. The answer is 125.
[Question]A conference center has six rooms. Each room can hold up to 80 people. Today, the conference center is only 2/3 full. How many people are in the conference center?
[Answer]The conference center can hold up to 80 x 6 = 480 people. Today, there are 480 x 2 / 3 = 320 people in the conference center. The answer is 320.
Q: There are 30 spaces for each vehicle in a parking lot. A caravan takes up a total of 2 spaces of parking space. How many vehicles can still park if there are 3 caravans currently parking?
A: The three caravans used up 3x2 = 6 parking spaces in the parking lot. Therefore, 30 - 6 = 24 vehicles can still park in the parking lot. The answer is 24.
Question: Erwan went on shopping. He purchased a pair of shoes at $200 but discounted 30%, and two shirts at $80 each. Upon checkout, the cashier said that there is an additional 5% discount. How much did he spend after all the discounts?
Answer:
The total discount of a pair of shoes is $200 x 30 / 100 = $60. He spent $200 - $60 = $140 for a pair of shoes. The total cost of two shirts is $80 x 2 = $160. The initial cost of his purchase is $140 + $160 = $300. He got an additional $300 x 5 / 100 = $15 discount upon checkout. Therefore, Erwan spent $300 - 15 = $285 after all the discounts. The answer is 285.