The diagram shows a semi-circle inside a rectangle of length 120 m - OCR - GCSE Maths - Question 20 - 2017 - Paper 1

The circumference of a full circle is given by the formula:

$C = 2\pi r$

For the semi-circle, the formula becomes:

$C_{semi-circle} = \pi r = \pi \times 60 \text{ m} = 60\pi \text{ m}$

Calculating this using a value for (\pi):

$C_{semi-circle} \approx 60 \times 3.142 = 188.4 \text{ m}$

The perimeter of the shaded region consists of the straight edges of the rectangle and the semi-circle:

$P = \text{Length of rectangle} + C_{semi-circle} = 120 ext{ m} + 188.4 ext{ m} = 308.4 ext{ m}$

Rounding this to three significant figures gives:

$P \approx 308 ext{ m}$