Question Details

The volume of a cube is four times the volume of a cuboid. If the sides of the cuboid are 32 cm, 8 cm and 4 cm, then find the ratio of the total surface area of the cube to that of the cuboid.

Options

A

3 : 4

B

24 : 13

C

24 : 32

D

21 :13

Show Answer

Correct Answer :

Option B

24 : 13

Solution :

The correct answer is Option 2: 24 : 13.

Step 1: Calculate the volume of the cuboid
The dimensions of the cuboid are given as:
Length (l) = 32 cm
Breadth (b) = 8 cm
Height (h) = 4 cm
The volume of a cuboid is calculated using the formula: Volume = l×b×h.

Volume of cuboid = 32 × 8 × 4 = 1024 cm 3

Step 2: Calculate the volume and side length of the cube
It is given that the volume of the cube is four times the volume of the cuboid.

Volume of cube = 4 × 1024 = 4096 cm 3

Let the side of the cube be a. The volume of a cube is given by a3.

a3 = 4096

Taking the cube root on both sides:

a = 40963 = 16 cm

Step 3: Calculate the total surface area of the cube
The total surface area of a cube is given by the formula: 6a2.

Total surface area of cube = 6 × (16)2 = 6 × 256 = 1536 cm 2

Step 4: Calculate the total surface area of the cuboid
The total surface area of a cuboid is given by the formula: 2(lb+bh+hl).

Total surface area of cuboid = 2 × (32×8+8×4+4×32)

= 2 × (256+32+128)

= 2 × 416 = 832 cm 2

Step 5: Find the required ratio
We need to find the ratio of the total surface area of the cube to that of the cuboid.

Ratio = 1536 832

Dividing both numerator and denominator by their common factor (64):

Ratio = 24 13

Thus, the ratio of the total surface area of the cube to that of the cuboid is 24 : 13.

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