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Did not understand the solution to this Ratio problem

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by stormier » Fri Jan 28, 2011 6:33 pm
madhan_dc wrote:Problem: A students grade in a course is determined by 4 quizzes and one exam. If the exam counts twice as much as each of the quizzes, what fraction of the final grade if determined by the exam?

can someone please explain a solution.

answer is 1/3
The problem says that an exam counts twice as much as a quiz. In other words, the weighting for exam is twice that of the quiz.

So if the student takes total of 4 quizzes and 1 exam, one can say that he took 6 quizzes (all of equal importance or weighting)

Out of these 6 quizzes which count equally towards the grade, 2 are determined by the exam.

Thus required fraction = 2q/(4q+1e) = 2q/(4q+2q) = 1/3
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by Anurag@Gurome » Sat Jan 29, 2011 12:48 am
madhan_dc wrote:Problem: A students grade in a course is determined by 4 quizzes and one exam. If the exam counts twice as much as each of the quizzes, what fraction of the final grade if determined by the exam?
One exam is equivalent to two quizzes.
Hence, total = (1 exam + 4 quizzes) = 6 quizzes

Required fraction = (1 exam)/(total) = (2 quizzes)/(6 quizzes) = 1/3
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by pesfunk » Sat Jan 29, 2011 2:57 am
Let the weight of one quiz be X

So total weight of all 4 quizzes = 4X

Weight of Exam = 2X (Given)

So total weight = 4X + 2X = 6X

Answer = 2X / 6X = 1/3
madhan_dc wrote:Problem: A students grade in a course is determined by 4 quizzes and one exam. If the exam counts twice as much as each of the quizzes, what fraction of the final grade if determined by the exam?

can someone please explain a solution.

answer is 1/3
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by GMATGuruNY » Sat Jan 29, 2011 3:57 am
madhan_dc wrote:Problem: A students grade in a course is determined by 4 quizzes and one exam. If the exam counts twice as much as each of the quizzes, what fraction of the final grade if determined by the exam?

can someone please explain a solution.

answer is 1/3
An easy and efficient approach would be to plug in values that satisfy the conditions given.

Let quiz = 1 point, exam = 2 points.
Quiz points = 4*1 = 4.
Exam points = 1*2 = 2.
Total points = 4+2 = 6.
Exam/total = 2/6 = 1/3.
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by madhan_dc » Sat Jan 29, 2011 5:47 am
Thank you all.
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