A = /360 x r²
If A= 15m² and = 90° . Find r
Please help, I don't know how to work backwards
The shape is a sector
$\displaystyle A=\frac{\theta}{360^{\circ}}\times \pi r^2$
They give you A and $\displaystyle \theta$...
So plugging them into the equation, you have
$\displaystyle 15~m^2=\frac{90^{\circ}}{360^{\circ}}\times \pi r^2$
Now just solve the equation for r:
$\displaystyle 15~m^2=\tfrac{1}{4}\pi r^2\implies 60 ~m^2=\pi r^2\implies r=\dots$
Try to figure out the rest.
I hope this helps!
--Chris