The last 3 students had an average completion time of 35 seconds so the sum of their completion times was 3 * 35 = 105 seconds. All 4 students (now including the student who came first) had an average completion time of 30 seconds, meaning the sum of their completion times is 4 * 30 = 120 seconds. The student who came first spent 120 - 105 = 15 seconds in the race.
The answer: 15
Reverse engineering the question: 4 students participated in a 200m race. If the average completion time of the last three students was 35 seconds, and the average completion time of all four runners was 30 seconds, how long (in seconds) did it take the student who came first to finish the race?


Reasoning and answer: The cubs need 140 pounds a week because 4 x 35 = 140. The family needs 350 pounds a week because 210 + 140 = 350. The family needs 50 pounds a day because 350 / 7 = 50. She needs to hunt 10 rabbits a day because 50 / 5 = 10.
The answer: 10
What was the question?
Question: A bear is hunting for her cubs and herself. She needs 210 pounds of meat in a week. Each cub needs 35 pounds a week and she has 4 cubs. She hunts rabbits, which are five pounds each. If she hunts daily, how many rabbits does she need to catch each day?


The hay previously cost $15 per bale so 10 bales would cost $15 * 10 = $150. Double 10 bales is 10 * 2 = 20 bales. Better quality hay cost $18 per bale so 20 bales would cost $18 * 20 = $360. Farmer Brown would need $360 - $150 = $210 more.
The answer: 210
Reverse engineering the question: Chester must deliver ten bales of hay to Farmer Brown. Farmer Brown wants Chester to supply better quality hay and double the delivery of bales of hay. If the previous hay cost $15 per bale, and the better quality one cost $18 per bale, how much more money will Farmer Brown need to meet his own new requirements?


Reasoning and answer: If the third school had 200 students, and the second school had 40 more students than the third school, the second school had 200 + 40 = 240 students. The third and second schools had 240 + 200 = 440 students on stage taking part in the debate. Since the first school had twice as many students as the second school, and the second school had 240 students, the first school had 240 * 2 = 480 students on stage taking part in the debate. If after the debate was over, every student at the stage shook the mayor's hand, the number of students who shook the mayor's hand is 480 + 440 = 920 students.
The answer: 920
What was the question?
Question: There were students from three different schools taking part in a debate organized by the town's mayor on a stage. The first school had twice as many students as the second school, and the second school had 40 more students than the third school. If the third school had 200 students, and after the debate was over, every student shook the mayor's hand, calculate the total number of students who shook the mayor's hand on the stage.


Jace drives a total of 4 + 9 = 13 hours. Jace will travel 60 * 13 = 780 miles.
The answer: 780
Reverse engineering the question: Jace drives 60 miles per hour. If Jace drives for 4 hours straight, take a 30-minute break, and then drives for another 9 hours straight, how many miles will he travel?


One chair costs $140 x 1 / 7 = $20. Four chairs cost $20 x 4 = $80. So a table and 4 chairs cost $140 + $80 = $220.
The answer: 220
Reverse engineering the question:
A chair costs 1/7 of the cost of a table. If a table costs $140, how much will it cost to buy a table and 4 chairs?