i found this on the stack exchange and thought that maybe someone on here could have a different opinion..
http://i.stack.imgur.com/ur9h2.jpg
the way i see it there's at least 3 answers to this problem due to the ambiguity of the question (and to the fact that the teacher didn't answer the original question!):
1. 15 minutes, using the teacher's method. it took 10 minutes to saw the board into two pieces, therefore it'll take 15 minutes to be sawed into 3 pieces.
2. 10 minutes, using the 'vague' interpretation. the question clearly says "if she works just as fast," and that implies that "work" would be the same amount of time is put in to cut the board into 3 pieces, which would be 10 minutes since it took 10 minutes to saw the board into 2 pieces.
3. 20 minutes, using the student's method. he/she was thinking very practically here. 1 cut makes 2 pieces, which takes 10 minutes. 2 cuts would give you 3 pieces (because you're dividing one of the cut boards into two, therefore having 3 pieces), which would take another 10 minutes. total time is 10 + 10 = 20 minutes.
i'm thinking number 3 is the right answer, the student was correct, and the teacher was wrong.. but what do you think?
http://i.stack.imgur.com/ur9h2.jpg
the way i see it there's at least 3 answers to this problem due to the ambiguity of the question (and to the fact that the teacher didn't answer the original question!):
1. 15 minutes, using the teacher's method. it took 10 minutes to saw the board into two pieces, therefore it'll take 15 minutes to be sawed into 3 pieces.
2. 10 minutes, using the 'vague' interpretation. the question clearly says "if she works just as fast," and that implies that "work" would be the same amount of time is put in to cut the board into 3 pieces, which would be 10 minutes since it took 10 minutes to saw the board into 2 pieces.
3. 20 minutes, using the student's method. he/she was thinking very practically here. 1 cut makes 2 pieces, which takes 10 minutes. 2 cuts would give you 3 pieces (because you're dividing one of the cut boards into two, therefore having 3 pieces), which would take another 10 minutes. total time is 10 + 10 = 20 minutes.
i'm thinking number 3 is the right answer, the student was correct, and the teacher was wrong.. but what do you think?
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the teacher is incorrect based on the wording of the problem
it takes 10 minutes to make 1 cut
1 board to two pieces is 1 cut
to make 3 pieces from 1 board, you need 2 cuts..
10 min per cut
20 min
it takes 10 minutes to make 1 cut
1 board to two pieces is 1 cut
to make 3 pieces from 1 board, you need 2 cuts..
10 min per cut
20 min
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The only logical answer is 3), 20 minutes.
To cut the board into 2 pieces requires making a SINGLE cut. So it takes here 10 minutes to make a SINGLE cut. To cut a board into 3 pieces would require 2 cuts, so if she can make one cut in 10 minutes, then 2 cuts takes twice as long: 20 minutes.
No other interpretation makes sense.
To cut the board into 2 pieces requires making a SINGLE cut. So it takes here 10 minutes to make a SINGLE cut. To cut a board into 3 pieces would require 2 cuts, so if she can make one cut in 10 minutes, then 2 cuts takes twice as long: 20 minutes.
No other interpretation makes sense.