If a cube with diagonal 7√3 cm is melted to form a cuboid, what will be its height, if the length of the cuboid is equal to the side of the cube and the width of the cuboid is 3.5 cm.

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RPF SI (2018) Official Paper (Held On: 19 Dec, 2018 Shift 1)
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  1. 6 cm
  2. 12 cm
  3. 14 cm
  4. 8 cm

Answer (Detailed Solution Below)

Option 3 : 14 cm
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Detailed Solution

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Given:

A cube with a diagonal of 7√3 cm is melted to form a cuboid. The length of the cuboid is equal to the side of the cube, and the width of the cuboid is 3.5 cm.

Concept:

The diagonal of a cube is given by the formula: d = a√3, where 'a' is the side of the cube.

The volume of the cube is equal to the volume of the cuboid formed.

Formula Used:

Diagonal of cube: d = a√3

Volume of cube: V = a3

Volume of cuboid: V = l × w × h

Calculation:

We have,

⇒ Diagonal of cube = 7√3 cm

⇒ a√3 = 7√3

⇒ a = 7 cm

Volume of the cube:

⇒ V = a3

⇒ V = 73

⇒ V = 343 cm3

Volume of the cuboid:

⇒ V = l × w × h

⇒ 343 = 7 × 3.5 × h

⇒ 343 = 24.5h

⇒ h = 343 / 24.5

⇒ h = 14 cm

∴ The height of the cuboid is 14 cm.

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