Question

the perimeter of a semi-circle is 90cm.Calculate its area
@ganeshie8
@girlover

Answer 1

that's wrong @botype

Answer 2

according to the book it is 481.25

Answer 3

but how?

Answer 4

@sleepyjess

Answer 5

@sleepyjess @Directrix

Answer 6

ummmmmmmmmmm.......... @pooja195

Answer 7

if u had a pic it would be easier to help

Answer 8

only the wording was given

Answer 9

The perimeter or circumference of a circle is given by C = 2 * pi * r

You have half a perimeter in the semicircle so 90 = pi * r

Answer 10

Solve this for r: 90 = pi * r

Then, you can use the area of a circle formula to get the area of the semicircle assuming the semicircle is "closed off" by a diameter.

Answer 11

6300/22?

Answer 12

@ChiefArnav -->Solve this for r: 90 = pi * r

Answer 13

How did you get this: 6300/22?

Answer 14

90 = 22/7 x r
r = 90 x 7/22
r = 6300/22
r= 286.36

Answer 15

Okay, next use the area formula

Area semicircle = .5 * pi *r^2

Put your value of r in the formula and crank out the area of the semicircle.

Answer 16

why .5?

Answer 17

Because we are finding the area of half of the circle.

Answer 18

Calculate its area

I assume that "its" refers to the semicircle.

Do you think "its" refers to the entire circle? Check your problem source.

Answer 19

then why not
pi*r^2/2?

Answer 20

Same thing. Use that if you like. But do not square the 2 when you square the radius.

Answer 21

Post your answer so we can compare.

Answer 22

22/7*28636/100*28636/100?

Answer 23

all over 2

Answer 24

What does that crank out to be?

Answer 25

wait

Answer 26

?

Answer 27

i got 5154111

Answer 28

That is not what I got.

Answer 29

can you TYPE out your work?

Answer 30

No. And, if I did and it looked like this: 22/7*28636/100*28636/100 then it would still make no sense to me.

Answer 31

i'm confused:(

Answer 32

What did you get for the radius of the semicircle?

Answer 33

286.36cm

Answer 34

I got r = 28.648 for the radius

Answer 35

oh,no worries i got the right ans:)

Answer 36

That is what this gives: 90 = 22/7 * r
so you should get the same thing for r.

Answer 37

For the area of the semicircle, you used this:

p i * ( (r^2) / 2 )

Answer 38

Which gives the same answer I got:

http://www.wolframalpha.com/input/?i=pi+*+%28+%2828.648%5E2%29+%2F+2+%29

@ChiefArnav