GMAT Quant

[Joy Shaha]

Q. A dishonest milkman purchased milk at 10 per liter, mixed 5 liters water in it. By selling the mixture at the rate of 10 per liter he earns a profit of 25%. Find the total amount of mixture that he sold
A. 20
B. 25
C. 50
D. none

[regor60]

Let X stand for the amount of milk purchased in liters at 10 units of cost per liter. So his total cost is

10X

Since he added 5 liters of water to the X liters of milk he sold

X + 5 liters of mixture, and at 10 units price per liter, his sales revenue is

10*(X + 5) = 10X + 50 units

His profit is

Sales revenue - Cost = 10X + 50 - 10X = 50

His profit as a percentage of cost is

50/10X

and since we're told that equals 0.25

50/10X = 0.25

Therefore, X = 20, so the total mixture sold is 20 + 5 = 25

[GMATGuruNY]

Q. A dishonest milkman purchased milk at 10 per liter, mixed 5 liters water in it. By selling the mixture at the rate of 10 per liter he earns a profit of 25%. Find the total amount of mixture that he sold
A. 20
B. 25
C. 50
D. none

We can PLUG IN THE ANSWERS, which represent the amount of sold mixture.
Start with the middle value.

B: 25 liters of sold mixture, implying 20 liters of purchased milk
Since the selling price for the mixture = $10 per liter, the total revenue for 25 liters of mixture = 25*10 = $250.
Since the cost of the purchased milk = $10 per liter, the total cost for 20 liters of purchased milk = 20*10 = $200.
Profit = (total revenue) - (total cost) = 250-200 = $50.
Profit/Cost = 50/200 = 1/4 = 25%.
Success!

The correct answer is B.