Final answer:
To find the area of the semi-circle with radius 4 cm, we use the formula ½(πr²) and round the result to one significant figure, resulting in approximately 25.1 cm². The circumference is found using the formula (πr + 2r), equaling approximately 20.6 cm. The radius is 4 cm and the diameter is 8 cm.
Step-by-step explanation:
The question is asking to find the area and circumference of a semi-circle with a given radius. It seems there is a typo mentioning 'medias' which should be 'radius,' and '200m' which is irrelevant to the problem since we have the radius as 4 cm. Let's clarify this first:
A semi-circle is half of a circle, so to find the area of a semi-circle with a radius 'r', we use the formula for the area of a full circle ½(πr²), where π is approximately 3.14159. Since the value of π is taken to many significant digits, the final answer should be rounded to the same number of significant digits as the given radius 'r'.
In this case, since the radius 'r' has only one significant figure, the area of the semi-circle should be rounded to one significant figure:
½(π×4²) = ½(π×16) ≈ ½(50.26548) ≈ 25.1 cm² (after rounding to two significant figures).
For the circumference of the semi-circle, we use half the circumference of the full circle plus the diameter, which is given by the formula (πr + 2r). Using the same rounding rules, since the radius is given as 4 cm, we find that the circumference is:
(π×4 cm + 2×4 cm) ≈ (12.56636 cm + 8 cm) ≈ 20.6 cm (after rounding to three significant figures).
Lastly, the radius is already given as 4 cm, and the diameter is simply twice the radius, so it's 8 cm.