A machinist creates a washer by drilling a hole through the center of a circular piece of metal. If the piece of metal has a radius of x + 10 and the hole has a radius of x + 6, what is the area of the washer?
A.x^2-8pie x-64 pie
B.x^2=8pie x 64pie
C.8pie x-64 pie
D.8pie x +64pie

Question

A machinist creates a washer by drilling a hole through the center of a circular piece of metal. If the piece of metal has a radius of x + 10 and the hole has a radius of x + 6, what is the area of the washer?
A.x^2-8pie x-64 pie
B.x^2=8pie x 64pie
C.8pie x-64 pie
D.8pie x +64pie

campbell_st · Answer

Area of Washer = Area of Metal - Area of the hole

$$A = \pi (x+10)^2 - \pi(x+6)^2$$

this will expand to 

$$A = \pi(x^2 + 20x + 100 - x^2 - 12x -36)$$

collecting like terms

$$A=\pi(8x + + 64)$$

or $$A=8\pi(x + 8)$$

anonymous · Answer

wait im lost

campbell_st · Answer

this uses the area of a circle 

$$A = \pi r^2$$

circular metal disk has a radius x + 10

               Hole                   radius  x + 6

washer area = area of the metal disk - area of the hole... 

just substitute and simplify