First find how many liters of the seawater are salt: 2 liters * 20% = .4 liters. Then multiply that amount by 1000 ml / liter to find the number of ml of salt Jack gets: .4 liters * 1000 ml / liter = 400 ml.
The answer: 400
Reverse engineering the question: Jack is stranded on a desert island. He wants some salt to season his fish. He collects 2 liters of seawater in an old bucket. If the water is 20% salt, how many ml of salt will Jack get when all the water evaporates?


Reasoning and answer: When Carla was waiting on Monday she counted 38 ceiling tiles and on Tuesday she counted them twice, 38 ceiling tiles x 2 = 76 times she counted a ceiling tile. She also counted 75 books in the room on Monday and counted them three times in a row on Tuesday, 75 books x 3 = 225 times she counted a book. On Tuesday Carla counted the ceiling tiles 76 times + counted books 225 times = 301 times Carla counted something on Tuesday.
The answer: 301
What was the question?
Question: To pass the time while she is waiting somewhere Carla likes to count things around her. While she is waiting for school to start on Monday she counts the tiles on the ceiling--38. While she is waiting for everyone to finish their tests after she has handed in hers, she counts the books in the room--75. On Tuesday Carla counts all the tiles twice in a row and she counts the books three times in a row when she has to wait for a long time for the teacher to finish handing out the graded tests. If every time Carla counts something counts as once, how many times has Carla counted something on Tuesday?


Flora has 50 * 2 = 100 books. Gary has 50 / 2 = 25 books. Together they own 100 + 25 + 50 = 175 books.
The answer: 175
Reverse engineering the question: Harry has 50 books in his library. His sister Flora has twice as many books and their cousin Gary has half the books Harry has. How many books do the three of them own together?


Reasoning and answer: There are 80 * 5 = 400 engines in total. 400 / 4 = 100 of the engines are defective. 400 - 100 = 300 of the engines are not defective.
The answer: 300
What was the question?
Question: If one fourth of the engines are defective, and there are 5 batches of 80 engines each. How many engines are not defective?


198 passengers / 9 buses = 22 passengers fit in one bus. 22 passengers / bus * 5 buses = 110 passengers fit in 5 buses.
The answer: 110
Reverse engineering the question: 198 passengers fit into 9 buses. How many passengers fit in 5 buses?


Joey Chestnut ate 75 hotdogs to claim the record and Lisa has eaten 20 hot dogs so far, so she still needs to eat 75 - 20 = 55 hotdogs to tie Joey Chestnut. Lisa has a 10 minute time period to eat the hotdogs and half the time has already passed, which means Lisa has 10 / 2 = 5 minutes left until the competition is over. If she needs to eat 55 hotdogs to tie Joey Chestnut and there are 5 minutes left in the competition period then she needs to eat 55 / 5 = 11 hot dogs per minute to have a chance of tying for a win.
The answer: 11
Reverse engineering the question:
Lisa is looking to attempt a World Record. She has decided to try and match Joey Chestnut's record of eating 75 full hotdogs, buns included, in 10 minutes. Halfway through the time Lisa has eaten 20 hotdogs. How many hotdogs will she have to eat per minute to at least tie Joey Chestnut's record?