First find the circumference of the whole circle using Pi x diameter. Halve the answer and add the diameter.
Thus: 3.1416 × 10 = 31.416 ÷ 2 + 10 = 25.708cm
So the perimeter of the semi-circle is 25.7cm
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diammeter*pi= 10 divide both side by pi to find the diameter: diameter = 3.183098862 or 3 cm to the nearest cm.
To find the distance around a figure, you calculate the perimeter. The perimeter is the total distance around the outside of a shape or figure. To find the perimeter of a rectangle or square, you add up all the sides. For a circle, you can find the perimeter by multiplying the diameter by π (pi).
πr² is the formula for finding the area of a circle. To find the area of a semicircle just divide the answer by two. So take the radius, square it, which in this case would be 100, multiply it by π [pi (3.14)] and divide it by two.
Well, darling, a semicircle is half of a circle, so to find the area you just take the area of a full circle and divide it by 2. The formula for the area of a circle is πr^2, so for a 10cm semicircle, you'd calculate it as 0.5 * π * 5^2, which gives you an area of 39.27 square centimeters. Voilà!
Is the 30ft the radius or the diameter. The area of a circle = Pi x (radius squared), so, if the diameter is 30ft, making the radius 15ft, the area would be Pi x(15 squared) square feet, and the area of its semicircle would be half of that, so the area required = Pi x (15 squared) divided by 2 = 353.429 sq ft On the other hand, if the diameter is 15ft, making the radius 7.5ft then the area required = Pi x (7.5 squared) sq ft for the full circle and half as much for the semicircle = 88.3573 sq ft As an extra; you will find that the area of the smaller semicircle is exactly one quarter of that of the larger semicircle, and I wonder if you can reason out why that is so.