Heather left the hospital and drove toward the desert at an average speed of 35 km/h. danielle left sometime later driving in the opposite direction with an average speed of 50 km/h. after heather had driven for four hours they were 290 km apart. how long did danielle drive

Danielle drove 3 hours

Step-by-step explanation:

Suppose Heather moved in the x direction.

Then Danielle moved in the opposite direction, that is, she moved in the -x direction.

Let's call , , at the speed, distance and time that I code Heather

Let's call , , at the speed, distance and time Danielle codes.

Observe the following diagram:

(x) Heather <------ --------- hospital ---------- -----------> Danielle (-x)

So:

We know that after 4 hours the distance between Heather and Danielle was 290 km.

That is to say:

We know that

We already know , the distance from the hospital to Heather, so we can find and thus know

So:

Then:

do you have any choices

step-by-step explanation:

$20.01

step-by-step explanation:

the sale price is (1.00 - 0.77)($87), or 0.23($87), or $20.01.