Problem Solving

Hey guys, I need some help with this problem. If anyone could help me out I would appreciate it very much. Here it is:

A certain car averages 25 miles per gallon on gasoline when driven in the city and 40 miles per gallon when driven on the highway. According to these rates, which of the following is closest to the number of miles per gallon the car averages when it is driven 10 miles in the city and 50 miles on the highway?

28
30
33
36 **Answer**
38

On a side note I just want to thank everyone for the help that I have received. I appreciate all the help. The GMAT from what I have learned preparing for the test can be quite frustrating. It helps ease ones spirits when one can come on this site and see that others are going through similar situations and ask for help. Thank you again.

Treat this like an average speed question.

Averages Miles Per Gallon = (Total Miles)/(Total Gallons gas used)

Total Miles = 60

Total Gallons gas used = Gallons Gas used in city + Gallons Gas used on Highway

In the city the car gets 25 miles/g or 1 g/25 miles

(1/25)*(10)= 10/25 = 2/5 gallons used in city

Using equivalent reasoning for the highway:

(1/40)*(50) = 50/40 = 5/4 gallons used on highway

Total Gallons gas used = 2/5 + 5/4 = 8/20 + 25/20 = 33/20

Averags Miles Per Gallon = (60)/(33/20) = (60)*(20)/(33) = 1200/33 = 36.3