Question

An airplane flew for 8 hours at an airspeed of x miles per hour (mph), and for 7 more hours at 325 mph. If the average airspeed for the entire flight was 350 mph, which of the following equations could be used to find x ?
A. x + 325 = 2(350)
B. x + 7(325) = 15(350)
C. 8x – 7(325) = 350
D. 8x + 7(325) = 2(350)
E. 8x + 7(325) = 15(350)

Answer 1

E. 8x+7(325)=15(325)

It would include the 8 hrs. of x miles per hour and the 7 hrs. of 325 miles per hour, giving the total miles. Then, as you eliminate, you can find out what (x) is.