mikemcgarry wrote:
guerrero25 wrote:
A dishonest person wants to make a profit on the selling of milk. He would like to mix water (costing nothing) with milk costing 33 $ per litre so as to make a profit of 20% on cost when he sells the resulting milk and water mixture for 36$. In what ratio should he mix the water and milk?
(A) 1:20
(B) 1:10
(C) 1:8
(D) 1:4
(E) 1:2
Dear
guerrero25,
I'm happy to help with this.
First of all, let's consider 1 liter of the stuff he is going to sell --- naive customers think it's pure milk, but we know it's some milk-water mixture. He is going to sell this liter of milk-water for $36.
This $36 should be a 20% increase over cost. Here, we need to think about percentage increases as multipliers. See this blog for more info:
https://magoosh.com/gmat/2012/understand ... -the-gmat/Using multipliers
(cost)*1.20 = $36
cost = 36/1.2 = 360/12 = $30
If he wants a 20% increase over cost on the sale of one liter of his milk-water, the cost has to be $30.
Well, a liter of milk costs $33, so if he is going to use just $30 of milk in his mixture, that's 30/33 = 10/11 of a liter. If milk is 10/11 of the liter, then water is 1/11 of the liter, and the ratio of water to milk is 1:10. Answer choice
(B)Does all this make sense?
Mike
Approached this question as follows -
He needs to make a profit of 20%, which means he needs to sell the milk +water combination for 39.6 (20% of 33 +33)
Now, he plans to sell 1 liter of this solution of milk and water for 36. which means he needs to sell 1.1 liters of this solution to earn 39.6. (36 for 1 liter and so 39.6 for 1.1 liters)
Hence the water added would be .1 liter.
Therefore the ratio of water to milk is .1/1 = 1/10
Please suggest if this approach is correct. Thanks