Question icon
9 grade maths

The length, breadth and height of a rectangular parallelepiped are in the ratio 6:3:1. If the surface area of a cube is equal to the surface area of this parallelepiped, then what is the ratio of volume of cube to volume of parallelepiped?

  • A. 1:1
  • B. 5:4
  • C. 7:5
  • D. 3:2

Profile image of Aniket Singh
11 Months agoGrade
Answers icon

1 Answer

Profile image of Askiitians Tutor Team
ApprovedApproved Tutor Answer11 Months ago

The problem involves a rectangular parallelepiped with dimensions in the ratio of 6:3:1. Let's denote the length, breadth, and height as 6x, 3x, and x respectively.

Calculating Surface Area

The surface area (SA) of a rectangular parallelepiped is given by the formula:

SA = 2(lb + bh + hl)

Substituting the dimensions:

SA = 2(6x * 3x + 3x * x + x * 6x)

This simplifies to:

SA = 2(18x² + 3x² + 6x²) = 2(27x²) = 54x²

Surface Area of the Cube

Let the side length of the cube be 'a'. The surface area of the cube is:

SA = 6a²

Setting the surface areas equal gives:

6a² = 54x²

From this, we can solve for 'a²':

a² = 9x²

Thus, a = 3x.

Calculating Volume

The volume (V) of the rectangular parallelepiped is:

V = l * b * h = 6x * 3x * x = 18x³

The volume of the cube is:

V = a³ = (3x)³ = 27x³

Finding the Volume Ratio

Now, we can find the ratio of the volume of the cube to the volume of the parallelepiped:

Volume Ratio = Volume of Cube : Volume of Parallelepiped = 27x³ : 18x³

This simplifies to:

Volume Ratio = 27 : 18 = 3 : 2

Final Answer

The ratio of the volume of the cube to the volume of the parallelepiped is 3:2. Therefore, the correct option is D.