A plane can fly 300 miles in the same times as it takes a ca

A plane can fly 300 miles in the same times as it takes a car to go 140 miles. If the car travels 80 mph slower than the plane, find the speed of the plane.

Solution

Let the speed of the plane of S mph.

Then, speed of the car will be S-80 mph.

Now, we know that speed is directly proportional to distance when time is constant. Therefore, we can write:

S/300 = (S-80)/140

S/15 = (S-80)/7

7S = 15S - 1200

8S = 1200

S = 150

Hence, Speed of the plane is 150mph.