What Does It Mean?
Math brain teasers require computations to solve.
There was a body pump class that lasted a long time, but it always changed. The instructor was a very smart person and liked to throw puzzles at the students. About 15 minutes into the class, one kid asked how much time there was left in the class. He said: "Right now? Oh, I'd say seven." The kid was confused and knew the instructor was never going to tell anybody.
Another 5 minutes in, another kid asked how much time was left. The instructor said, "About five now." Confused, the kid went back and the class continued.
Ten minutes later, a perplexed pupil in the front asked how much time was left. The instructor said, "I think it's about three."
Suddenly, the pupil clicked into what the puzzle was and how much time there was left of the class and how long the class was.
How much time was left of the class?
Answer
90 minutes.
When the first student asked, 15 minutes in, the instructor said "Seven". 15 times 7 is 105, the amount of time left in the class.
The second student asked 5 minutes later (20 minutes in) and the instructor said "Five." 20 times 5 is 100, the number of minutes left in the class.
The last student got "Three" when he asked again, at the 30 minute mark. 30 times 3 is 90, the number of minutes left in the class and the answer to this brain teaser.
The class was two hours long.
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Comments
mathgirl
Aug 24, 2011
 Nice one! I got it right too! 
Sassygurl
Sep 05, 2011
 Im really new so its nice to have a semihard one because i can try to figure it out! Nice teaser! 
Mathgeek007
Sep 05, 2011
 Thanks! Glad to know you like my teasers! 
zembobo
Sep 16, 2011
 If by "What Does It Mean?" you are referring to a "body pump class" then I'm stumped because unless it's aculteral thing, I have no idea what that is and I could not continue with this teaser because I was so stuck on that. FYI, next time just say Phys Ed or Gym class or something. 
Mathgeek007
Sep 16, 2011
 Body Pump is a class for lifting weights. >.> 
CrazyPineapple
Nov 12, 2011
 Hi math! I've been checking out your latest brainteasers and boy have you improved! I like your teasers a lot. They get better and better each time! 
stil
Jan 18, 2012
 The setup has too many absurdities. Since all the actors in this puzzle can apparently gauge time in minutes, a natural question is, "How many more minutes?" How does the instructor know everyone won't just walk away after 22 minutes? No "puzzle" would have been created if the second student had kept his mouth shut.
The solution seems more a matter of 'how much longer' than 'how much is left.' 
Jimbo
Oct 02, 2012
 How can anyone answer this? The answers given by the instructor are a function of how much time has already elapsed. We are not told this. It might as well have been based on the ages of his children or whatever. The fact that the answer works when you are given it and it is explained does not make it solvable. 
Mathgeek007
Apr 18, 2013
 It does make it solvable. Just because you couldn't solve it, doesn't make it not solvable. 
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