The way to do this is to measure the length of the arc. This is a simple ratio of the angle of the arc and the total angle (360 degrees or 2pi rad) multiplied by the total circumference of the circle. The formula if you are still unsure is this:

Ratio of angle Circumference
(Angle of arc / 2pi) * 2x pi x r.


This can be simplified to Angle of arc (in radians) * radius. Simplifying the equation with the total perimeter, you can find the radius of the circle. You should get 90m.

With this radius, you can now find the area of the land. Use the formula above, but instead of using the circumference formula, you use the area formula for the circle. You should get the answer. Give it a try, hope it helps