How do I solve and what is the answer?

Question

A plane can fly 1040 miles in the same time as it takes a car to go 400 miles. If the car travels 80 mph slower than the plane, find the speed of the plane.

Answer 1

Hi Katelyn,

 

Car drives 400 miles (D1)

Plane flies 1040 miles (D2)

 

car rate (R1) = plane rate (R2) - 80 mph

 

distance = rate * time

time = distance/rate

 

We know that the times are equal for both the plane and car.

therefore:

D1/R1 = D2/R2

Let's Substitute what we know:
400/(R2 - 80) = 1040/R2

 

Solve for R2:
400/R2 - 400/80 = 1040/R2

5 = (1040 - 400)/R2

5(R2) = 640

R2 = 128 mph (speed of plane)