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average weight

by alivapriyada » Wed Sep 29, 2010 11:03 pm
What is the average weight of the class?
A. The ratio of the average weight of all the boys and girls is 3:2
B. The number of boys and girls in the class are 40 and 60 respectively

[spoiler]OA later
[/spoiler]
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by ashokkadam » Thu Sep 30, 2010 12:08 am
alivapriyada wrote:What is the average weight of the class?
A. The ratio of the average weight of all the boys and girls is 3:2
B. The number of boys and girls in the class are 40 and 60 respectively

[spoiler]OA later
[/spoiler]
Statement 1 is insufficient, so we are left with B,C,E
Statement 2 is insufficient, so we are left with C,E

Together, sufficient so answer is C.

This is a question on Weighted averages.
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by alivapriyada » Thu Sep 30, 2010 2:23 am
ashokkadam wrote:
alivapriyada wrote:What is the average weight of the class?
A. The ratio of the average weight of all the boys and girls is 3:2
B. The number of boys and girls in the class are 40 and 60 respectively

[spoiler]OA later
[/spoiler]
Statement 1 is insufficient, so we are left with B,C,E
Statement 2 is insufficient, so we are left with C,E

Together, sufficient so answer is C.

This is a question on Weighted averages.
i dont think that C will work.could you plz explain it a bit more??
Will give the OA soon.
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by ashokkadam » Thu Sep 30, 2010 2:36 am
Average weight of the class = (Total weight of boys + Total weight of girls) / (Total number of boys + Total number of girls)

Since we cannot calculate the total weight, E has to be the answer.......hehehe ;)
alivapriyada wrote:
ashokkadam wrote:
alivapriyada wrote:What is the average weight of the class?
A. The ratio of the average weight of all the boys and girls is 3:2
B. The number of boys and girls in the class are 40 and 60 respectively

[spoiler]OA later
[/spoiler]
Statement 1 is insufficient, so we are left with B,C,E
Statement 2 is insufficient, so we are left with C,E

Together, sufficient so answer is C.

This is a question on Weighted averages.
i dont think that C will work.could you plz explain it a bit more??
Will give the OA soon.
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by alivapriyada » Thu Sep 30, 2010 2:57 am
ashokkadam wrote:Average weight of the class = (Total weight of boys + Total weight of girls) / (Total number of boys + Total number of girls)

Since we cannot calculate the total weight, E has to be the answer.......hehehe ;)
alivapriyada wrote:
ashokkadam wrote:
alivapriyada wrote:What is the average weight of the class?
A. The ratio of the average weight of all the boys and girls is 3:2
B. The number of boys and girls in the class are 40 and 60 respectively

[spoiler]OA later
[/spoiler]
Statement 1 is insufficient, so we are left with B,C,E
Statement 2 is insufficient, so we are left with C,E

Together, sufficient so answer is C.

This is a question on Weighted averages.
i dont think that C will work.could you plz explain it a bit more??
Will give the OA soon.
lets wait for some more options.
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by monusangeeta » Thu Sep 30, 2010 10:45 pm
Hi,

My answer is also E. My approach was:

Statement 2: Totall Insuf, says nothing about weights
Statement 1: Insuf, Avg B: Avg G = 3:2 => Actual Avg B and G = 3x, 2x, Still we dont know no. of Girls and boys

Combining both, Statment 1 needs 3 variables: x, no. of boys and no. of girls, Statement 2 provides values for 2 variables: no. of boys and no. of girls. however, value of variable x is still missing. For diff value of x, there will be diff value of avg weight of the class. Insuff.

E wins.

Thanks
monusangeeta
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by kvcpk » Thu Sep 30, 2010 11:40 pm
alivapriyada wrote:What is the average weight of the class?
A. The ratio of the average weight of all the boys and girls is 3:2
B. The number of boys and girls in the class are 40 and 60 respectively

[spoiler]OA later
[/spoiler]
Average weight = total weight of class/ strength of class

A. The ratio of the average weight of all the boys and girls is 3:2
avg weight of boys = total wt of boys/number of boys = TWB/NB
similarly avg wt of girls = TWG/NG
We are given that TWB/NB * (NG/TWG) = 3/2
We do not know any particualr value to proceed further. hence INSUFF

B. The number of boys and girls in the class are 40 and 60 respectively
INSUFF because it doesnt speak about weights at all.

Combining:
NB = 40
NG = 60
Hence from stmt1,
TWB/40 * 60/TWG = 3/2
Hence, TWB = TWG
Total weight of class = TWB+TWG
Strength of class = 6+40 = 100
Hence avg = 2(TWB)/100 = TWB/50

Still we do not know TWB or TWG or TWC

Hence INSUFF

pick E.
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by alivapriyada » Thu Sep 30, 2010 11:45 pm
OA E. kudos to all!!!
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by sumit.sinha » Fri Oct 01, 2010 5:33 am
alivapriyada wrote:What is the average weight of the class?
A. The ratio of the average weight of all the boys and girls is 3:2
B. The number of boys and girls in the class are 40 and 60 respectively

[spoiler]OA later
[/spoiler]
What is Total Weight/ Total students?
OR (Total weight Boys + total Weight Girls)/ (total boys + total girls)
i.e ( Tb+Tg)/(b+g)? ------------------(1)

(1) Ab/Ag = 3/2
(Tb*g)/(Tg*b) = 3/2
Substituting in (1)
3/2 (Tg)
Since we don't know weight of total girls (or boys for that instance). Insufficient

(2) b= 40, g = 60
Insufficient

(1) and (2) together
as b+g cancel each other out in Statement (1), knowing the number of boys and girls are still not sufficient, we need to know the total weight of girls or boys.

Pick E.
Cheers,
Sumit
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by GMATGuruNY » Fri Oct 01, 2010 9:03 am
alivapriyada wrote:What is the average weight of the class?
A. The ratio of the average weight of all the boys and girls is 3:2
B. The number of boys and girls in the class are 40 and 60 respectively

[spoiler]OA later
[/spoiler]
The easiest -- and perhaps safest -- approach is to plug in twice.

Statements 1 and 2 together:
Plug in that each boy weighs 3 pounds, each girl 2 pounds.
Total weight of boys = 40*3 = 120
Total weight of girls = 60*2 = 120
Average = 240/100 = 2.4

Plug in that each boy weighs 6 pounds, each girl 4 pounds.
Total weight of boys = 40*6 = 240
Total weight of girls = 60*4 = 240
Average = 480/100 = 4.8

Since the average can be 2.4 or 4.8, insufficient.

The correct answer is E.
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by goyalsau » Sat Oct 02, 2010 3:08 pm
alivapriyada wrote:What is the average weight of the class?
A. The ratio of the average weight of all the boys and girls is 3:2
B. The number of boys and girls in the class are 40 and 60 respectively

[spoiler]OA later
[/spoiler]
I would like to add just one thing.
we are looking for average weight and no weight is given so should be E,
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