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

OF COURSE...25%

AS ONLY 1 CUT IS MADE....

AND WHOLE BOX HAS COLOURED.....

JUST EXCEPT THAT SIDE

IT HAS 4 SIDES ....

3 SIDES ARE PAINTED....

MEANS 1 SIDE IS NOT PAINTED

MEANS 1/4*100 =25%

Answer 2

Answer:

25%

Step-by-step explanation:

Number of surfaces in a cube = 6

Let the surface area of each surface = 6

Therefore, the surface area of the cube = 6x (See figure 1 at the attachment for reference)

The cube is cut in the middle into two rectangular solids of equal volume. (See figure 1.1 and figure 1.2 at the attachment for reference)

Considering each of the new solids,

No. Of surfaces = 6

Surface area of 2 surfaces(right and left) = x + x = 2x

Surface area of the remains 4 surfaces = 4 * (1/2)x = 2x

Therefore, the surface area of each of the new rectangular solids = 2x + 2x = 4x

Surface area of each of the new solids is not painted red = x (Refer the figures at the attachment for clarity)

Therefore, the percent of the surface area of each of the new solids is not painted red:

4x = 100

x = 25%