Question

what is the area of the semicircle? 20 mm 157 mm² 62.8 mm² 125.6 mm² 314 mm²

Explanation:

Step1: Find the radius.

The diameter is 20 mm, so the radius $r=\frac{20}{2}=10$ mm.

Step2: Calculate the area of the full - circle.

The formula for the area of a circle is $A = \pi r^{2}$. Substituting $r = 10$ mm, we get $A=\pi\times(10)^{2}=100\pi$ $mm^{2}$.

Step3: Calculate the area of the semi - circle.

The area of a semi - circle is half of the area of the full - circle. So $A_{semicircle}=\frac{1}{2}\times100\pi = 50\pi$ $mm^{2}$. Taking $\pi\approx3.14$, we have $A_{semicircle}=50\times3.14 = 157$ $mm^{2}$.

Answer:

157 $mm^{2}$