ssriva2 wrote:
monikaleoster wrote:
How much water should the milkman add to milk purchased by him for $20/- to get 50% profit?
(1) He has 1 litre of milk.
(2) He wishes to sell the diluted milk at $25 a litre.
In this gmat like questions,what will be more appropriate choice C or E?
PLEASE HELP!
Dear
ssriva2,
My friend, I am happy to help.
I see that there is a lot of discussion on this question, but not a solution. I will show it here.
Since you are asking about
(C) vs.
(E), I will assume that you recognize that each statement alone is insufficient. Also, note: we are assuming that water is free. I believe virtually everywhere in the world, tap water of these quantities, a liter or two, is essentially free. Yes, if I am going to build a housing development that will use millions of gallons daily, I need to think about water costs. If I am filling my liter water bottle from the tap, I don't need to think about water costs.
For this calculation, it will be helpful to think about rates, because this is similar to work rates:
https://magoosh.com/gmat/2012/gmat-work-rate-problems/Let's consider both statements together. We know he has a liter of milk, so he has spent $20---that's his cost. To get a 50% profit, he would have to have a revenue of $30.
If he is going to sell the diluted milk at $25/L, then to make a revenue of $30, he would have to sell ($30)/($25/L) = (6/5) L = 1.2 L. Well, he has a liter of milk, so he need to add 0.2 liters of water so that he winds up with 1.2 L of the diluted milk. That would sell for $30, which would give him a 50% profit.
With both statements combined, we can come to an exact numerical answer. Together the statements are sufficient. OA =
(C).
Actually, for a problem such as this, yes, it's important to understand how to work the full solution, but in a DS set-up it's also an important skill to recognize that one
could find the numerical answer, without actually doing all the calculations. That's what was happening in many of the responses above. Understanding how to do the calculations is very important, but ultimately, mastery of GMAT DS involves seeing that one
could do the full solution without having to do every step of it.
Does all this make sense?
Mike
_________________
Mike McGarry
Magoosh Test PrepEducation is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)