Kap 800 question

gmat_2007 wrote:I don't understand this kap 800 (even with the explanation!)

A abtch of cookies was divided among three tins: 2/3 of all the cookies were placed in either the blue tin, and the rest were palced in the red tin. If 1/4 of all the cookies were palced in the blue tin, what fraction of the cookies that were placed in the other tines were placed in the green tin?

My quess was: number of cookies in the green tin
-----------------------------------------------------------------
no. of cookies in blue tins + no.of cookies in the red tin

But the answer is arrived at by:
number of cookies in the green tin
-------------------------------------------------------------- no. of cookies in green tin + no.of cookies in the red tin

I'm missing a basic concept of fractions here, but can't figure which..

chatekar wrote:Assuming what Sadowski said is correct, explanation would go like this

Suppose there are 60 cookies in all.
2/3 of these cookies (40), go into either blue or green tin.

so Cookeis in blue tin + cookies in green tin = 40 ----------------[1]

Remaining (20), go into the red tin

so cookies in red tin = 20

Now 1/4 of the total cookeis (15) go into blue tin,

so cookies in blue tin = 15 -------------------[2]

Using [1] and [2],

Cookies in green tin = 25

Now the asked fraction = (cookies in green tin) / (total cookies)

Fraction = 25/60 = 5/12

I hope I'm making some sense to you
What the correct answer?

Thanks
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