OpenStudy (anonymous):

Is this the correct formula: ( = pi*r^2) or this one A=1/2*pi*r^2 @jim_thompson5910 @ganeshie8

3 years ago
OpenStudy (vishweshshrimali5):

1/2*pi*r^2

3 years ago
OpenStudy (anonymous):

With the first equation I got 40 , with the 2nd equation I got 20.

3 years ago
OpenStudy (jim_thompson5910):

How did you get 40?

3 years ago
OpenStudy (anonymous):

Check the question title, that's why I'm asking which equation is correct...

3 years ago
OpenStudy (jim_thompson5910):

What's the diameter of this semi-circle?

3 years ago
OpenStudy (anonymous):

I already did all that : The two radius' are 5 and 3.5 . I just don't know which formula is correct! If the 1st formula in the title is correct than the answer would be 40, if the 2nd formula in the title is correct than the answer would be 20 instead.

3 years ago
OpenStudy (jim_thompson5910):

A = pi*r^2 is the area of a whole circle A = 1/2*pi*r^2 is the area of half a circle

3 years ago
OpenStudy (anonymous):

Ah! That's why.. ------------- I solved it these two ways: 1st equation $A =\pi*5^2$ $A= 78.539 \approx 78.54$ $A =\pi*3.5^2$ $A= 38.48$ $78.53-38.48=40.05$

3 years ago
OpenStudy (jim_thompson5910):

ok now you can cut that answer in half since you only want the upper half (not the entire circle)

3 years ago
OpenStudy (anonymous):

Now, if you use the second equation it would imply the answer is 20 .

3 years ago
OpenStudy (jim_thompson5910):

good

3 years ago
OpenStudy (anonymous):

:D Yay.

3 years ago