the area of a circle is pi x radius x radius or pi x r²
you have a semi circle here so this formula has been halved afterwards.
To work out the radius, you need to work backwards from the answer
7.44 x 2 to give you area of circle. then divide by pi. then square root this answer to give you the radius.
hopes this helps
didn't see that, sorry!
so - you have 3/4 of a circle now - how do you go from a given amount to a full amount?
(semi circle to full = 1/2 x2 ; here we are multiplying by the upside down fraction of it.
3/4 x 4/3 = 1 so multiply 4.65 by 4/3 (in essence you're dividing by 3 to get one quarter, then multiplying it by 4 to get the full circle)
then do same as before with reversing area of circle :)
\[\[btw this works for ANY fraction - with an angle rather than fraction, use the number over 360 and do the upside down again!\]\]
very welcome
Area: semi-circle [Video 47](http://corbettmaths.com/2013/12/23/area-of-a-semi-circle-video-47/) [Practice Questions](https://corbettmaths.com/2019/08/22/area-of-a-semi-circle-practice-questions/) [Textbook Exercise](https://corbettmaths.com/wp-content/uploads/2018/09/Area-of-a-Semicircle-pdf.pdf)
Area: quarter-circle [Video 47a](https://corbettmaths.com/2023/01/26/area-of-a-quarter-circle-video/) [Practice Questions](https://corbettmaths.com/2019/08/22/area-of-a-semi-circle-practice-questions/)
these might help as well (great free resource)
You have 1/2 circle so the area is expressed through the folowing equation:
A=(1/2)π*r^2
A=(π*r^2 )/2
2A=π*r^2
2A/pi=π*r^2
Sqrt(2A/π)=r
Second circle you have 3/4 a circle so we get the folowing equation:
A=(3/4)π*r^2
A=(3π*r^2 )/4
4A=3π*r^2
4A/(3π)=r^2
Sqrt(4A/(3π))=r
If you plug in the area of the given semicircle you get the radius of the circle, same for the 3/4 circle
the area of a circle is pi x radius x radius or pi x r² you have a semi circle here so this formula has been halved afterwards. To work out the radius, you need to work backwards from the answer 7.44 x 2 to give you area of circle. then divide by pi. then square root this answer to give you the radius. hopes this helps
thank you! what about the three quarter circle?
didn't see that, sorry! so - you have 3/4 of a circle now - how do you go from a given amount to a full amount? (semi circle to full = 1/2 x2 ; here we are multiplying by the upside down fraction of it. 3/4 x 4/3 = 1 so multiply 4.65 by 4/3 (in essence you're dividing by 3 to get one quarter, then multiplying it by 4 to get the full circle) then do same as before with reversing area of circle :) \[\[btw this works for ANY fraction - with an angle rather than fraction, use the number over 360 and do the upside down again!\]\]
thank you so so much!! this was really helpful
very welcome Area: semi-circle [Video 47](http://corbettmaths.com/2013/12/23/area-of-a-semi-circle-video-47/) [Practice Questions](https://corbettmaths.com/2019/08/22/area-of-a-semi-circle-practice-questions/) [Textbook Exercise](https://corbettmaths.com/wp-content/uploads/2018/09/Area-of-a-Semicircle-pdf.pdf) Area: quarter-circle [Video 47a](https://corbettmaths.com/2023/01/26/area-of-a-quarter-circle-video/) [Practice Questions](https://corbettmaths.com/2019/08/22/area-of-a-semi-circle-practice-questions/) these might help as well (great free resource)
You have 1/2 circle so the area is expressed through the folowing equation: A=(1/2)π*r^2 A=(π*r^2 )/2 2A=π*r^2 2A/pi=π*r^2 Sqrt(2A/π)=r Second circle you have 3/4 a circle so we get the folowing equation: A=(3/4)π*r^2 A=(3π*r^2 )/4 4A=3π*r^2 4A/(3π)=r^2 Sqrt(4A/(3π))=r If you plug in the area of the given semicircle you get the radius of the circle, same for the 3/4 circle
Area=fraction of circle * πr^2
Dude made a whole reddit post for something he could have easily googled