How many gallons of water should be added to make the

Question

How many gallons of water should be added to make the average value of the mixture $480 per gallon.

(1) 5 gallons of Milk type I is mixed with 6 gallons of Milk type II.
(2) Milk of type I is $600 per gallon and the cost of type II Milk is 90% of the cost of Milk of type I.

KarishmaB · Accepted Answer

The question says that a mixture has milk type I and milk type II and now we need to add water to make the average value = $480. So how much water needs to be added?

To find the volume of water, you need to know the price of all three - milk type I, milk type II and water. You also need the volume in which milk type I and milk type II were added.

B alone isn't sufficient because it just gives you the price of milk type I and type II. We don't know the volume of these two. Even when you have both statements 1 and 2, you do not know the price of water (which may not be assumed to be available free of cost)

KarishmaB · Answer

Generally water is assumed to be available free of cost but it is an assumption. The writer of the question is probably testing whether you make that assumption. You should not, in a DS question. Had it been a PS question, and an answer was required, you could have assumed it.

nov79 · Answer

IMO E. In the answers whater si not mentioned so we can not say how mach whater is needed...

MichelleSavina · Answer

thank you nov79....

but i guess that is what we are suppose to find..... Can someone please explain it in another way....

144144 · Answer

hmm. why is it not B? if u know the prices per gallon, u know how much water u need to add to each one in order to make them worth 480.

or the questions is how much when milk I + Milk II is mixed?

144144 · Answer

Ye, thats ez. i thought they might be asking you to reduce the price of each one of them. Thanks.

jlgdr · Answer

Hm.. that's confusing cause I remember doing a question where I had to assume that water was free of cost and it was correct anyway. I'll take it into account from now on Cheers! J

EMPOWERgmatRichC · Answer

Hi All,

Is information missing from the prompt? Based on the two Facts, it appears that we're meant to mix two types of milk with water, but without information in the prompt to establish what the 'parameters' of the question are, this prompt is essentially nonsense.

GMAT assassins aren't born, they're made,
Rich

AjChakravarthy · Answer

If we assume that water is free, then the answer is C. ?

KarishmaB · Answer

Yes, then you can solve it.

Avg Price = (Price1 * w1 + Price2 * w2 + Price3 * w3)/(w1 + w2 + w3)

480 = (600*5 + 540*6 + 0)/(5 + 6 + w)

Solve for w, the amount of water added.

shriramvelamuri · Answer

Hi karishma

I did exactly the same way as you did, but realised that the assumption of cost of water is not warranted.

I hope question such as this would be on real test.. So Equivocal... the answer shifts from C to E.

Vinayprajapati · Answer

Assumed water available free of cost and got C.

praneet87 · Answer

Have there been instances where we need to make such assumptions? that water costs money too?

hellosanthosh2k2 · Answer

Good Question, Teased me

I answered C assuming water is free of cost. Need to bring in CR techniques in DS as well.

Madhavi1990 · Answer

But doesn't it say PER GALLON? So essentially B says --> 600 + 540 = $1140 for just milk (say 2 gallons). So one gallon (total) would be 1140/2 which is $570. So to bring it down to $480, we would know how much dilution is required PER GALLON? (Sorry for caps, just trying to emphasize, not yell

). Also, in questions where water price (or anything else) is not to be assumed? Thank you!

Madhavi1990 · Answer

Oh yes, I did assume its free, and picked B.

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