How do you find this missing car MPG?

Question

I drove 100 miles and got 30 MPG. Next, I drove 500 miles. I got a total of 40 MPG for the total 600 miles. What was my MPG for the 500 miles?

What formula did you use? Thank you very much.

Answer 1

600 miles/40 miles/gallon = 600 miles x 1 gallon/40 miles = 15 gallons

 

100 miles/30 miles/gallon = 3 1/3 gallons

 

15 - 3 1/3 = 11 2/3 = 35/3 gallons

 

500 miles/(35/3) gallons = 500 miles x 3/(35 gallons) = 1500/35 mpg = 42 30/35 = 42 6/7 mpg