Full circle
Circumference = 2*pi * r
Circumference = pi * d
Area = pi r * r = pi * r^2
Area = pi d^2 / 4
Half circle
Circumference = pi * r
Circumference = pi * r / 2
Area = pi r^2 / 2
Area = pi d^2/8
The answer depends on what you are looking for and what you are given. But those are the only common formulas I can think of at the moment.
No . because you would then have 2/4 which is 1/2 50%
the answer would be b the answer is 114
18. Set the the two equations equal and solve.
To get 51/60 courted to decimal you simply divided 51 by 60