Question

Help with geometry questions?!??

Answer 1

If line AB, across the window, measures 25 inches, calculate the area of the window in square inches.

Answer 2

line AB is the diameter,can u find the radius of window?

Answer 3

yes, 12.5

Answer 4

correct :) now area of circle is pi*r*r where r u got as 12.5
can u find area?

Answer 5

what did you get?

Answer 6

i got 490.87 square inches...u calculated it?

Answer 7

that's what i got, i'm just confused because the answers are all in terms of pi.

Answer 8

oh wait, is it 156.25 pi?

Answer 9

yup ,it is :)

Answer 10

when you do pi*r*r
if you just do the r*r part and leave it pi* Whatever r*r is
you get their answer

Answer 11

okay great! I have another question too...

Answer 12

If line AB, across the window, measures 18 inches, calculate the area of semicircle ACB in square inches.

Answer 13

people often leave pi (instead of multiplying it out) because that is an exact answer.

Answer 14

semicircle is 1/2 of a whole circle

Answer 15

yes... so do we find the circumference of the whole circle first?

Answer 16

calculate the area

Answer 17

It is almost the same problem as before: from the diameter get the radius. from the radius (and pi) get the area
then say, semicircle is 1/2 the whole circle, so its area is 1/2 of what I just found

Answer 18

is it 9 pi?

Answer 19

what is r?
what is pi*r*r
what is pi*r*r/2 ?

Answer 20

r is 9

Answer 21

remember the area of a circle is
\[ A= \pi r^2 \]

Answer 22

254.46

Answer 23

You probably want to leave pi in, so just 81 pi

Answer 24

It depends on what answer choices they give you.

Answer 25

and since it's a semi circle.... 40.5 pi?

Answer 26

yes. Does it make sense?

Answer 27

yes! and how do you find the circumference? because i need to know that too!

Answer 28

A different formula
\[ C= 2 \pi r\]
or, because 2*r= d (the diameter) you also might see
\[ C= \pi d\]
Personally, I use the first because memorizing different equations for the same thing is too much! So, before going to sleep, say C equals two pi are (10 times)

Answer 29

18 pi?

Answer 30

C= 18 pi when r=9
or about 56.55 if they want a number.

Answer 31

thank you!!