plane can fly 260 miles in the same time as it takes a car to go 100miles as the car travels 80mph slower find the speed of the plane.

Question

I know the formula to use but am very confused on how to set it up

Answer 1

Lets say the rate of the plane is x then the rate of the car is x-80. 

 

We know their times are equal so you will solve for time for each.

 

The time for the plane is

 

d/r=t

 

The distance the plane traveled is 260 miles. The distance the car traveled is 100.

 

The time for both are equal so the distance/rate of the plane = distance/rate of the car

 

We said the rate for the plane was x and the rate of the car was x-80.  Now we just plug in

 

d/r(plane) = d/r (car)  Ignore the parentheses except to differentiate what they are. 

 

260/x = 100/(x-80)

 

you will cross multiply to get

 

260x - 20800= 100x

 

Subtract 260x to take it to the other side and you will get

 

-20800=-160x

 

x = 130 The speed of the plane.