Question

HELP W? ACT PREP: The figure below shows 2 tangent circles such that the 10-centimeter diameter of the smaller circle is equal to the radius of the larger circle. What is the area, in square centimeters, of the shaded region?
DRAWN BELOW

Answer 1

Which part is shaded? :)

Answer 2

the larger circle only

Answer 3

Inside the big circle, but outside the small one? ah ok

Answer 4

yep

Answer 5

That's not too bad :)
That's simply
`the area of the big circle` - `area of the small circle`

Answer 6

You'll have to recall your area formula:
\(\large\rm A=\pi r^2\)
What is the area of the larger circle?
Are you able to figure that out based on the information given?

Answer 7

yes! so it would be two equations, one pi (10)^2 and then the other pi(10)^2?

Answer 8

Ooo careful! :)
They didn't actually tell us the `radius` of the smaller circle.

Answer 9

oh yeah ok so what do i do?

Answer 10

You have to remember the relationship bebtween `diameter` and `radius`.

Answer 11

radius is half diameter

Answer 12

Ok good :o
Half of 10 is 5.
So that gives us the `r` that we want to use for the smaller circle.

Answer 13

yes

Answer 14

You had your first equation correct,
which corresponded to the area of the larger circle
\(\large\rm \pi(10)^2\)

Answer 15

So the smaller one, which we've corrected, should be
\(\large\rm \pi(5)^2\)
ya? :o

Answer 16

yes

Answer 17

Square those numbers,
then subtract the smaller one from the larger one

Answer 18

i forget do i use pi in the equation orr just leave it until the end

Answer 19

ok nevermind for my final answer i got 75pi

Answer 20

yay good job \c:/

Answer 21

thanks