myhelper: RD Sharma 2020 solution class 9 chapter 18 Surface Area and Volume of a Cuboid and Cube VSAQS

RD Sharma 2020 solution class 9 chapter 18 Surface Area and Volume of a Cuboid and Cube VSAQS

VSAQS

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Question 1:

If two cubes each of side 6 cm are joined face to face, then find the volume of the resulting cuboid.

Answer 1:

We have,

Side of each cube (a) = 6 cm

We need to find the volume of resulting cuboid

Hence, dimensions of the resulting cuboid are,

Length (l) = 2a

Breadth (b) = a

= 6 cm

Height (h) = a

= 6 cm

Hence, volume of the resulting cuboid,

Hence, volume of the resulting cuboid is.

Question 2:

Three cubes of metal whose edges are in the ratio 3 : 4 : 5 are melted down in to a single cube whose diagonal is $12 \sqrt{3}$ cm. Find the edges of three cubes.

Answer 2:

The edges of the three cubes are in the ratio 3 : 4 : 5.

So, let the edges be 3x cm, 4x cm, 5x cm.

The diagonal of new cube is

We need to find the edges of three cubes

Here, volume of the resulting cube,

Let,

Edge of the resulting cube

So, diagonal of the cube, so

Hence,

Now;

The edges of the three cubes are,

The edges of the three cubes are .

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Question 3:

If the perimeter of each face of a cube is 32 cm, find its lateral surface area. Note that four faces which meet the base of a cube are called its lateral faces.