Question

The distance d that a car can travel in a certain amount of time t can be found by multiplying the rate of speed r by the travel time. If a car has already travel 4 miles, the formula for the total distance travel is d= rt + 4. Which of the following gives the value of r, in terms of d and t?

Answer 1

Answer:$r=\frac{d-4}{t}$

If the formula of the the total distance travel is:

$d=rt+4$    (1)

And we want to know the value of $r$ in terms of $d$ and $t$, we have to clear $r$ from equation (1):

$d-4=rt$    

$r=\frac{d-4}{t}$>>>>This is the value of $r$

Answer 2

Answer:

$r=\dfrac{d-4}{t}$

Explanation:

The formula for the total distance travel is

$d=rt+4$

We need to find the value of r, in terms of d and t.

Subtract 4 from both sides.

$d-4=rt+4-4$

$d-4=rt$

Divide both sides by t to find the value of r.

$\dfrac{d-4}{t}=\dfrac{rt}{t}$

$\dfrac{d-4}{t}=r$

Interchange both sides.

$r=\dfrac{d-4}{t}$

Therefore, the value of r, in terms of d and t is $r=\dfrac{d-4}{t}$.