A store sells milk in cartons of two sizes, one-half gallon

[BTGmoderatorLU]

Source: GMAT Prep

A store sells milk in cartons of two one-half gallon and one-quarter gallon. If the store sold a total of 300 cartons of mild yesterday, how many gallons of milk did it sell yesterday?

1) Yesterday the store sold 120 one-quarter-gallon cartons of milk
2) Yesterday the store sold 90 gallons of milk in one-half-gallon cartons

The OA is D

[nitink]

Let the number of half-gallon carton be h and quarter-gallon carton be q

Given h + q = 300

From 1 : q=120, so h =300-120 = 180
since we know the no. of individual cartons sold, so we can find out the total no. of gallons of milk sold.

From 2:
1/2 * h = 90
h= 180
so, q =120

As in 1, since we know the no. of individual cartons sold, so we can find out the total no. of gallons of milk sold.

So D.