The ping pong balls cost 10000 * .10 = $1000. So the discount is 1000 * .30 = $300. So he pays 1000 - 300 = $700.
The answer: 700
Reverse engineering the question: Ping pong balls sell for $.10 each. Johnny buys 10000 for a prank. He gets a 30% discount for buying in such large bulk. How much does he pay?


Reasoning and answer: If there are 20 surfers at Santa Monica, Malibu beach has twice as many surfers as Santa Monica has 2 * 20 = 40 surfers. Together, the two beaches have a total of 40 + 20 = 60 surfers.
The answer: 60
What was the question?
Question: There are twice as many surfers on Malibu beach as in Santa Monica beach. If there are 20 surfers in Santa Monica, calculate the total number of surfers on the two beaches.


They have $126 for helium because 200 - 42 - 18 - 14 = 126. They can buy 84 ounces of helium because 126 / 1.5 = 84. They can fly 9,492 feet up because 84 x 113 = 9,492.
The answer: 9492
Reverse engineering the question: Harry wants to build a homemade helium balloon with his son, Kevin, so he and Kevin go to the store with $200. They buy a giant sheet to turn into a balloon for $42, a rope for $18, and a propane tank and burner for $14. They plan to use the rest of the money on helium. The helium is $1.50 per ounce. For every ounce they buy, the balloon can fly 113 feet higher. How many feet up can they fly the balloon?


Reasoning and answer: Harry ran 10 x 50 / 100 = 5 meters per hour faster on Tuesday to Wednesday. So he ran 10 + 5 = 15 meters per hour from Tuesday to Thursday. Then on Friday, he ran 15 x 60 / 100 = 9 meters per hour more. Therefore, he ran 15 + 9 = 24 meters per hour on Friday.
The answer: 24
What was the question?
Question: Harry is joining a marathon that's why he practices and varies his workouts from day to day. He ran 10 meters per hour on Monday. From Tuesday to Thursday he ran 50% faster than on Monday. Then on Friday, he ran 60% faster than he ran on Thursday. How fast did Harry run on Friday?


The plant supplier earned $50 x 20 = $1000 for the orchids. He earned $25 x 15 = $375 for the potted Chinese money plants. So, his total earnings was $1000 + $375 = $1375. Then he paid $40 x 2 = $80 to his workers. He used a total of $80 + $150 = $230 for the worker's pay and new pots. Hence, he was left with $1375 - $230 = $1145 from his earnings.
The answer: 1145
Reverse engineering the question: A plant supplier was able to sell 20 pieces of orchids for $50 each and 15 pieces potted Chinese money plant for $25. The money he earned was then used to pay his two workers $40 each and to buy new pots worth $150. How much money was left from the plant supplier's earnings?


A quarter is worth five nickels because .25 / .05 = 5. She gets 100 nickels from the bank because 20 x 5 = 100. 20 of the nickels are iron nickels because 100 x .20 = 20. 80 of the nickels are regular because 100 - 20 = 80. The iron nickels are worth $60 because 20 x 3 = 60. The regular nickels are worth $4 because 80 x .05 = 4. Her money is now worth $64 because 60 + 4 = 64.
The answer: 64
Reverse engineering the question:
Alice has 20 quarters. She wants to exchange them for nickels and so she goes to the bank. After getting back from the bank, she discovers that 20% of the nickels are iron nickels worth $3 each. What is the total value of her money now?