It might help if the question indicated whether 5 cm referred to diameter or circumference or something else. Until then, the question cannot be answered and is simply a waste of everyone's time.
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it is half the diameter e.g 10cm diameter = 5 cm radius
Radius = 5/(2*pi) = 0.7958 cm rounded to 4 decimal places
radius = diameter ÷ 2 ⇒ radius = 10 cm ÷ 2 = 5 cm
A = 78.54 cm2
If the circumference of a circle is 12 cm the radius is: 1.91 cm