Question

A cube of white chalk is painted red, and then cut parallel to the sides to form two rectangular solids of equal volume. What percent of the surface area of each of the new solids is not painted red?

• A. $20\%$
• B. $16^{\frac{2}{3}}\%$
• C. $15\%$
• D. $25\%$

Answer 1

Answer: (D)

$25\%$

Answer 2

Let each side of the cube be 2 cm.
It is cut from the middle Then we have two cuboids of dimensions 2$\times$1$\times$1
One face in each is not coloured
Area of this face = 2$\times$2 = 4
Total surface area of one cuboid = 2(2$\times$2+2$\times$1$+$2$\times$1) =16
$\therefore$ Percent of area not painted $=\frac{400}{16}=25\%$
The correct option is (D): $25\%$