step by step
A=1/2h(B+b)
15=1/2h(4+1)
15/(4+1)=1/2h
15/5=1/2h
3=1/2h
h=2*3
h=6
The formula of an area of a circle:
We have
r = 1.8 m
π ≈ 3.14
Substitute: