4. A spotlight is on the ground 20 ft away from a wall and a 6 ft tall person is walking towards the wall at a speed of 3 ft/sec. How fast is the length of his shadow on the wall changing when the person is 8 feet from the wall?

2.5 ft/s

Step-by-step explanation:

As the triangles are similar we have

Again from the similar triangles we get

Differentiating with respect to time we get

The rate of change of the length of the shadow on the wall is 2.5 ft/s.

the area of the rectangle is 35units^2.

step-by-step explanation:

graph it and find the distance.

it is a 5*7 rectangle.

therefore the area is 35units^2.