I would choose A

in (2) we can not eliminate the number of male/females variable, and then we don't know the average

A is indeed correct answer as average weight is constant (140) for all examples.
Let Male be 1 and Females be 2, thus:
Total weight of Male = 180
Total weight of Females = 120*2 = 240
total weight = 420, Avg. = 420/3 = 140

You could use any values and result will still be same.

D cannot be correct answer because:
Answers would vary based on values:

If number of males equal 20 then as per statement two females would equal 30 hence average would be (3600 + 3600)/50 = 144.
Example two: Number of males equal 10 and females equal 20:
(1800 + 2400)/30 = 140

Hope this clarifies your doubt.

Thanks, it does clarifies my doubt.

albertrahul wrote:A is indeed correct answer as average weight is constant (140) for all examples.
Let Male be 1 and Females be 2, thus:
Total weight of Male = 180
Total weight of Females = 120*2 = 240
total weight = 420, Avg. = 420/3 = 140

You could use any values and result will still be same.

D cannot be correct answer because:
Answers would vary based on values:

If number of males equal 20 then as per statement two females would equal 30 hence average would be (3600 + 3600)/50 = 144.
Example two: Number of males equal 10 and females equal 20:
(1800 + 2400)/30 = 140

Hope this clarifies your doubt.

isn't this calculation wrong for fact stmt-1

As per the fact stmt-twice as many female as male=> M= 2F.

so the total no of female in terms of Male= 120/2= 60 or total no of Male in term of Female = 180*2= 360F

So, the total average weight= (360F+120F)/2F+F ==> 480F/3F=>160

In terms of Male----> (180M+60M)/M+M/2
240M/1.5M --->160.

Correct me if my calculation is wrong. I was little confused with the calculation of albertrahul. Though i found her approach correct along with the answer.

IMO it's A

Let number of Males be - M and Number of women be W

then what we are searching for is (M*180+W*120)/ (M+W)

In order to solve this we need to find the connection between M and W such that would remove this unknowns and leave us only with numbers.

It is obvious that A offers such connection. (If you plug in 2M instead of W)

While B doesn't, if you plug in M+10 instead of W then there is no way you can get rid of unknown M so you can not solve the problem.

Yeah, I know everybody loves plugging in numbers instead of algebraic solution but still... I think this one is easy this way too.

I might be missing something here but don't you guys think we can find the average of the whole lot without any of the options

average of males=180
average of females=120
average of the group=(180+120)/2=150

correct me if i am wrong

ok I got the flaw in my case..

tohellandback wrote:I might be missing something here but don't you guys think we can find the average of the whole lot without any of the options

average of males=180
average of females=120
average of the group=(180+120)/2=150

correct me if i am wrong

ok I got the flaw in my case..

No tohellandback that's exactly GMAT Trap!

Look at this :

Set 1 ( 1 2 3) average1=2

Set 2 ( 1 2 3 4) average2=5/2

Combined set ( 1 2 3 1 2 3 4 ) average 16/7


Now if we did this (av1+Av2)/2 then we would have average of 9/2 and that does not equal 16/7, i.e. this method of calculation is wrong.

To calculate the average of combined group correctly you need this steps

1. Av1 * 3 (3 is the number of values in set 1)

2. Av2*4 (4 is the number of values in set 2)

3. (1)+(2) = 16

4. (3)/(3+4) - where 3 and 4 are the number of values in the set1 and set2 respectively, ---- the result will be 16/7

ket wrote:

tohellandback wrote:I might be missing something here but don't you guys think we can find the average of the whole lot without any of the options

average of males=180
average of females=120
average of the group=(180+120)/2=150

correct me if i am wrong

ok I got the flaw in my case..

No tohellandback that's exactly GMAT Trap!

Look at this :

Set 1 ( 1 2 3) average1=2

Set 2 ( 1 2 3 4) average2=5/2

Combined set ( 1 2 3 1 2 3 4 ) average 16/7


Now if we did this (av1+Av2)/2 then we would have average of 9/2 and that does not equal 16/7, i.e. this method of calculation is wrong.

To calculate the average of combined group correctly you need this steps

1. Av1 * 3 (3 is the number of values in set 1)

2. Av2*4 (4 is the number of values in set 2)

3. (1)+(2) = 16

4. (3)/(3+4) - where 3 and 4 are the number of values in the set1 and set2 respectively, ---- the result will be 16/7

Thanks ket i got it.

by the way, before you could delete it, I had already seen your flawed post:))

yeah I deleted first post because I made errors in calculation, thats why I hate it plugging numbers! I always mess something up :)