Question

Calculate the area of the annulus which has an external diameter of 25cm and an internal diameter of 15cm

Answer 1

The correct answer is 314.159 square cm

Answer 2

314.159 square cm

Explanation:

Area of an annulus with external radius r1 and internal radius r2 is given by
π(r1² - r2²)

radius = half diameter

r1 = 25/2 = 12.5 cm

r2 = 15/2 = 7.5 cm

Area of annulus
= π(12.5² - 7.5²)
= 314.159 square cm