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ratio of average

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by success1111 » Tue May 05, 2009 1:17 am
What is the ratio of the average (arithmetic mean) height of students in class X to the average height of students in class Y?

(1) The average height of the students in class X is 120 centimeters.
(2) The average height of the students in class X and class Y combined is 126 centimeters.
Trust but verify.
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Re: ratio of average

by Vemuri » Tue May 05, 2009 7:55 am
success1111 wrote:What is the ratio of the average (arithmetic mean) height of students in class X to the average height of students in class Y?

(1) The average height of the students in class X is 120 centimeters.
(2) The average height of the students in class X and class Y combined is 126 centimeters.
IMO E.

We do not know the number of students in class X & class Y. This information is required to solve.
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by aj5105 » Thu May 14, 2009 11:38 pm
(E)
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by mikeCoolBoy » Fri May 15, 2009 1:03 am
I do not understand why the answer is not C

Average of class X = 120
Average of class Y = 132
ratio 120/132 = 10/11

I don't see why we need the number of students
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by ontopofit » Fri May 15, 2009 1:35 am
ans. is definitely C.
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by zuleron » Fri May 15, 2009 4:57 am
It is 120 + x / 2 = 126, what is x...

We don't need to know the number of students coz they give us the average of both classes.
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by zuleron » Fri May 15, 2009 5:46 am
It is 120 + x / 2 = 126, what is x...

We don't need to know the number of students coz they give us the average of both classes.
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by mike22629 » Fri May 15, 2009 8:40 am
No zuleron, you are misintrepretting the question I believe. It matters how many people are in x and y of the average of 126 when determining the average of y. If there is only one person, Y's average will be much higher than if there are 100 people.

For example,

100 People in x have a height of 120
100 People of y have a height of 132

Ratio = 120:132

Or 100 people in x have a height of 120
1 person has a height of (not sure but something very high) to make the average of both of them = 126.

Ratio = 120: (very high number)

IMO E.

Opinions? Not sure, just my opinion
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by vittalgmat » Fri May 15, 2009 11:07 am
IMO E as well.
We need to know the number of ppl in X and Y. otherwoise we cannot get the weighted average.
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by mikeCoolBoy » Fri May 15, 2009 11:31 am
I think you´re right answer should be E

I just read again the question and we don´t know weather the average of class Y is 132 or 129. I made a silly mistake assuming that the number was equal.
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