Question

A cube whose edge is 20 cm 1 point

long, has circles on each of its
faces painted black. What is the
total area of the unpainted
surface of the cube if the
circles are of the largest
possible areas?(a) 90.72 cm2 (b)
256.72 cm² (c) 330.3 cm² (d)
514.28 cm?

​

Answer 1

Unpainted surface area = 514.28 cm²

Explanation:

Given:

Side of cube = 20 Cm

Radius of circle = 20 / 2 = 10 Cm

Find:

Unpainted surface area

Computation:

Unpainted surface area = Surface area of cube - 6(Area of circle)

Unpainted surface area = 6a² - 6[πr²]

Unpainted surface area = 6[a² - πr²]

Unpainted surface area = 6[20² - π10²]

Unpainted surface area = 6[400 - 314.285714]

Unpainted surface area = 514.28 cm²