Question

In the time that it takes one car to travel 93 km, a second car travels 111 km. If the average speed of the second car is 12 km/h faster than the speed of the first car, what is the speed of each car?

Answer 1

`"Car 1" \ = \ "64 km/h"`

`"Car 2" \ = \ "74 km/h"`

Explanation:

The formula for speed is

`s=d/t`

For the first car, we know `d` and plugging it into the formula gives us

`s_1=93/t`

We know the second car is `"12 km/h"` faster and the distance is `"111 km"`, so the formula in terms of the first car's speed would be

`s_1+12=111/t=s_2`

Now we can solve for `s_1` in the second equation

`s_1=111/t-12`

Now we can set the two `s_1` equal to each other and solve for `t`

`93/t=111/t-12`

`93=111-12t`

`12t=18`

`t=3/2 \ "hours"`

Now we can plug `t` into the first car equation to solve for the speed of it

`s_1 = "93 km"/(3/2 \ "h") = "62 km/h"`

We know the second car is `"12 km/h"` faster, so

`"62 km/h" \ + \ "12 km/h" = "74 km/h"`