Question

Bob is taking his son to look at colleges. The first college they plan to visit is 150 miles from their home. In the first hour they drive at a rate of 60 mph. If they want to reach their destination in 2.5 hours, what speed must they average for the remainder of their trip? (I wouldn't mind if you use a proportion since that's how I'm supposed to solve it)

Answer 1

`60\ mph`

Explanation:

we know that

The speed is equal to divide the distance by the time

Let

s ----> the speed in mph

d ----> the distance in miles

t ----> the time in seconds

`s=(d)/(t)`

step 1

In the first hour they drive at a rate of 60 mph

Find the distance traveled

we have

`s=60\ mph`

`t=1\ h`

substitute

`60=(d)/(1)`

`d=60\ mi`

so

The remainder of the trip is equal to

`150\ mi-60\ mi=90\ mi`

step 2

Find out the average speed for the remainder of the trip

we have

`d=90\ mi\\t=2.5-1=1.5\ h`

substitute the values

`s=(90)/(1.5)=60\ mph`