Question

The diagram above shows a plan for a park. ABCD is a rectangle.

APB and DQC are semicircles centred at X and Y.
Given AB = 7 cm and AC = 25 cm.
Calculate the perimeter of the park in cm.​

Answer 1

Perimeter of the park = 70 cm

Explanation:

Perimeter of the park = perimeter of the 2 semicircles + 2(length of the rectangle)

Perimeter = 2πr + 2(BC)

✔️Perimeter of the 2 semicircles = 2πr

Where,

radius (r) = ½(AB) = ½(7)

r = 3.5 cm

Perimeter = 2*π*3.5 = 7*π

Perimeter of the two semicircles = 21.9911486 ≈ 22 cm

✔️Find BC using Pythagorean theorem:

Thus,

BC = √(AC² - AB²)

AC = 25

AB = 7

BC = √(25² - 7²) = √576

BC = 24

✔️Perimeter of the park = perimeter of the 2 semicircles + 2(length of the rectangle)

Perimeter of the park = 22 + 2(24)

= 22 + 48

= 70 cm