A cube whose each edge is 28 cm long has a circle of maximum radius on each of its face painted red. Find the total area of the unpainted surface of the cube.

Maximum diameter of circle can be 28 cm (Since, each edge is 28 cm).

So, radius = $\dfrac{28}{2}$ = 14 cm.

Area of each unpainted face = Area of square - Area of circle

= side² - πr²

= 28² - $\dfrac{22}{7} \times (14)^2$

= 784 - 616

= 168 cm².

Since, there are 6 faces in cube.

Total area of unpainted face = 6 × 168 = 1008 cm².

Hence, total area of unpainted surface = 1008 cm².