SOLUTION: A plane left Kennedy Airport on Tuesday morning for an 855-mile, 7-hour trip. For the first part of the trip, the average speed was 115 mph. For the remainder of the trip, the aver

Algebra ->  Percentages: Solvers, Trainers, Word Problems and pie charts -> SOLUTION: A plane left Kennedy Airport on Tuesday morning for an 855-mile, 7-hour trip. For the first part of the trip, the average speed was 115 mph. For the remainder of the trip, the aver      Log On


   

Question 1102922: A plane left Kennedy Airport on Tuesday morning for an 855-mile, 7-hour trip. For the first part of the trip, the average speed was 115 mph. For the remainder of the trip, the average speed was 125 mph. How long did the plane fly at each speed?
first part of trip is how many h   

second part of trip is how many h
Answer by josgarithmetic(39630) About Me  (Show Source):
You can put this solution on YOUR website!
The assignment of a variable for one of the times is implied here:

             SPEED      TIME      DISTANCE
Part 1        115         x        115x
Part 2        125        7-x     125(7-x)
Total                     7        855

highlight_green%28115x%2B125%287-x%29=855%29
Knowing how to form that equation and being able to solve it is all you need to understand.
SOLVE FOR x AND EVALUATE THE OTHER TIME QUANTITY.