Kiski wrote:

A convenience store currently stocks 48 bottles of mineral water. The bottles have two sizes of either 20 or 40 ounces each. The average volume per bottle the store currently has in stock is 35 ounces. How many 40 ounce bottles must be sold for the average volume per bottle to be reduced to 25 ounces if no 20 ounce bottles are sold?

A) 10

B) 20

C) 30

D) 32

E) 34

I managed to find the break up of 20 ounce and 40 ounce bottles respectively,but have gone west from there.Can someone have a look at this problem?Will post OA tomorrow.

Well this one is lengthy problem .

From the first we get

Let x be the number of 20 ounce bottle

So [20x + 40(48-x)]/48 = 35

Gives x= 12

Number of 20 ounce = 12

Number of 40ounce = 36

Let number of 40 ounce sold be y

so [ 20*12 + 40*(36 - y) ] / ( 48 -y ) = 25

which gives y = 32

So answer is D .