Acar is moving at a fixed speed. the distance d that the car covers is then directly proportional to the time t it moves. if d=20 miles when t=15 minutes, write a proportion to find d for t=20 minutes

We were told that the distance is directly proportional to the time .

We write this mathematically as,

We can now introduce our constant of variation and write the equation for the direct equation as;

where is the constant of variation or constant of proportionality.

We substitute and , in to the equation of variation to obtain the constant of proportionality.

That is;

This implies that,

This simplifies to give us,

Now our equation of proportion becomes,

When T=20

Writing this as a mixed number we obtain,

This can also be rewritten as

correct to one decimal places.

Therefore the care covers miles in minutes.