Question

1. perimeter (terms of pi) 6π + 12 perimeter (number) 30.8

Explanation:

Step1: Find the arc - length of the semi - circle

The formula for the circumference of a full circle is $C = 2\pi r$. For a semi - circle, the arc - length $l$ is $\frac{1}{2}\times2\pi r=\pi r$. Given the diameter $d = 12$ cm, the radius $r=\frac{d}{2}=6$ cm. So the arc - length $l=\pi\times6 = 6\pi$ cm.

Step2: Add the diameter to the arc - length

The perimeter $P$ of a semi - circle is the sum of the arc - length and the diameter. The diameter is 12 cm. So $P=6\pi + 12$ cm.

Step3: Calculate the numerical value

Substitute $\pi\approx3.14$ into $6\pi + 12$. Then $P=6\times3.14+12=18.84 + 12=30.84\approx30.8$ cm.

Answer:

Perimeter (terms of Pi): $6\pi+12$ cm
Perimeter (number): $30.8$ cm