Standard Mathematics Primary 6 Circles

A school garden has a semicircular flower bed of radius $14$ cm. The gardener wants to lay decorative edging around the WHOLE perimeter of the flower bed (the curved edge AND the straight edge). What total length of edging is needed? (Use $\pi = \dfrac{22}{7}$.)

A 72 cm
B 44 cm
C 88 cm
D 58 cm
Show Worked Solution

Worked Solution

Step 1: A semicircle is exactly half of a circle. Its perimeter has two parts: the curved arc, and the straight diameter that closes it.\n Step 2: Compute the arc length (half the circumference): arc = ½ × 2 × π × r = π × r = $\dfrac{22}{7} \times 14 = 44$ cm.\n Step 3: Compute the straight edge (the diameter): $d = 2 \times r = 2 \times 14 = 28$ cm.\n Step 4: Add the two parts to get the full perimeter: $44 + 28 = 72$ cm.\nCheck: 72 − 28 = 44 cm of arc; $44 \div \dfrac{22}{7} = 14$ cm = r. ✓ Answer: 72 cm

Correct answer: 72 cm

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