Averages-DS question

[kapitalist]

In a certain group of people, the average (mean) weight of the males is 180 lbs and of the females, 120 lbs. What is the average weight of the people in the group.

1) The group contains twice as many females as males

2) The group contains 10 more females than males


answer A

I thought at first you cant compare to averages together? but the answer choice says something different? Please explain the problem so the next time I see it I can know that it can be solved and move on. Thanks.

[gmat740]

Male Female
180 120
x 2x


avg = [x*180 + 2x*120] /x +2x

= 420x/3x
= 420/3
= 140

So, (I) is suff

II.

Male Female
180 120
x x+10

Avg = [x*180 + (x+10)*120]/x + x+10

= [30x + 1200]/2x+10

Unsolvable

So Insuff

Hence

Answer A

Hope this helps

Karan

[kapitalist]

thanks...

it was easier than I thought...I think i just had a brain fart. For some reason I have this notion that when AVG problems come up to be very skeptical on the choices because you are dealing with "averages."

[gmat740]

dont worry
Keep Practicing