Question

help! how do figure this out A plane can fly 300 miles in the same time as it takes a cr to go 120 miles. If the car travels90 mph slower than the plane, find the speed of the plane

Answer 1

ah ok. so you have some pieces of information that you need to turn into an equation you can solve

Answer 2

I'll give it a shot

Answer 3

thanks

Answer 4

so we have two basic variables, the speed of the plane, and the speed of the car

Answer 5

since the plane goes 320 miles in the same time the car goes 120 miles, the plane's speed (p) in relation to the car's speed is 320/120

Answer 6

that is:
1. p = 320/120 c

Answer 7

the second piece of information is that the car travels 90 mph slower than the plane

Answer 8

2. c = p - 90

Answer 9

now that you have two equations, and two variables, you can solve via subsitution

Answer 10

so for our case, let's take the value of (c) from the second equation, and substitute it for the (c) in the first equation

Answer 11

1. p = 320/120 c , if c = p - 90, is the same as:
2. p = (320 x (p - 90))/120
3. p = 8(p - 90)/3 (reducing the fraction part)
4. p = 8p - 720/3
5. 3p = 8p - 720
6. 5p = 720
7. p = 144

Answer 12

so the plane travels 144mph