Question

The dial on an old telephone is a plastic ring 8cm in diameter with a4cm diameter hole in the center. Ten small dialing holes each of diameter 1.2cm are cut out of the ring

Answer 1

Area of remaining plastic = 36.55 cm² (Approx.)

Explanation:

Given:

Diameter of plastic dial of telephone = 8 cm

Diameter of middle hole = 4 cm

Diameter of ten small holes = 1.2 cm

Find:

Area of remaining plastic

Computation;

Radius of plastic dial of telephone = 8/2 = 4 cm

Radius of middle hole = 4/2 = 2 cm

Radius of ten small holes = 1.2/2 = 0.6 cm

Area of remaining plastic = Area of plastic dial - Area of middle hole - 10[Area of small holes]

Area of remaining plastic = π(4)² - π(2)² - π(0.6)²

Area of remaining plastic = π(16) - π(4) - π(0.36)

Area of remaining plastic = π[16 - 4 - 0.36]

Area of remaining plastic = π[11.64]

Area of remaining plastic = (3.14)(11.64)

Area of remaining plastic = 36.5496

Area of remaining plastic = 36.55 cm² (Approx.)