Question

The figure below shows Daniel’s semi-circular patio. The shaded region represents the tiled portion of the patio.



The width of the tiled portion is 1.5 feet. What is the area of the tiled portion of the patio, rounded to the nearest whole square foot?


http://learn.flvs.net/webdav/assessment_images/educator_geometry_v14/pool_Geom_3641_0800_Subtest_03_14/image0024e67800f.jpg

Answer 1

Hint:

There are 2 semi-circles here. The larger one has a radius of 12/2 = 6 feet. The smaller one has a radius of 6 - 1.5 = 4.5 feet

Answer 2

The area of a semi-circle with the radius 'r' is

A = (pi*r^2)/2

Answer 3

So I do 3.14*4.5squared/2 and get 31.7925 and round it to 32??

Answer 4

that's the area of the smaller semi-circle

Answer 5

what's the area of the larger one?

Answer 6

and I would round at the very end

Answer 7

Okay so I get 56.52. Do I add the 2 areas together next?

Answer 8

no

Answer 9

you want the shaded area

Answer 10

that's equal to

Larger Area - Smaller Area

Answer 11

So 31.7925 - 56.52? But that gives me a negative number...

Answer 12

do it the other way around

Answer 13

larger minus smaller

Answer 14

Oh lol. :3 I knew that.

Answer 15

that's ok, happens to everyone

Answer 16

the answer is 25. Thanks so much. <3

Answer 17

you're welcome

Answer 18

you should have gotten 24.7275 which rounds to 25, so nice work

Answer 19

One question.. why do I have to divide by 2?

Answer 20

the area of a circle is

A = pi*r^2

the area of the semi-circle (or half circle) is exactly half that

So that's why we divide by 2

Answer 21

Okay thanks.

Answer 22

yw