Mensuration
- The perimeter of the floor of a room is 18 m. What is the area of the walls of the room, if the height of the room is 3 m ?
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Area of four walls of a room = 2(length + breadth) × height
= Perimeter of floor × height = 18 × 3 = 54 m²Correct Option: C
Area of four walls of a room = 2(length + breadth) × height
= Perimeter of floor × height = 18 × 3 = 54 m²
- The length (in metres) of the longest rod that can be put in a room of dimensions 10 m × 10 m × 5 m is
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Length of the longest rod Diagonal = √10² + 10² + 5² = √225 = 15 metre
Correct Option: B
Length of the longest rod Diagonal = √10² + 10² + 5² = √225 = 15 metre
- The floor of a room is of size 4 m × 3 m and its height is 3 m. The walls and ceiling of the room require painting. The area to be painted is
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Area of the four walls of the room = 2 × height (length × breadth)
= 2 × 3 (4 + 3) = 42 sq. metre
Area of ceiling = 4 × 3 = 12 sq. metre
∴ Total area = 42 + 12 = 54 sq. metreCorrect Option: B
Area of the four walls of the room = 2 × height (length × breadth)
= 2 × 3 (4 + 3) = 42 sq. metre
Area of ceiling = 4 × 3 = 12 sq. metre
∴ Total area = 42 + 12 = 54 sq. metre
- If the sum of three dimensions and the total surface area of a rectangular box are 12 cm and 94 cm² respectively, then the maximum length of a stick that can be placed inside the box is
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Let the length, breadth and height of the box be x, y and z cm respectively.
∴ x + y + z = 12 ...(i)
and 2 (xy + yz + zx) = 94 ...(ii)
∴ (x + y + z)² = x² + y² + z² + 2xy + 2yz + 2zx
⇒ 144 = x² + y² + z² + 94
→ x² + y² + z² = 144 – 94 = 50
∴ Maximum length of stick = √x² + y² + z²
= √50 = 5√2cmCorrect Option: A
Let the length, breadth and height of the box be x, y and z cm respectively.
∴ x + y + z = 12 ...(i)
and 2 (xy + yz + zx) = 94 ...(ii)
∴ (x + y + z)² = x² + y² + z² + 2xy + 2yz + 2zx
⇒ 144 = x² + y² + z² + 94
→ x² + y² + z² = 144 – 94 = 50
∴ Maximum length of stick = √x² + y² + z²
= √50 = 5√2cm
- If the length of the diagonal of a cube is 8√3cm, then its surface area is
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If the length of the edge of cube be x cm, then
diagonal = √3x cm
∴ √3x = 8√3 ⇒ x = 8cm
∴ Surface area of the cube = 6x² = 6 × 8 × 8 = 384 sq. cmCorrect Option: D
If the length of the edge of cube be x cm, then
diagonal = √3x cm
∴ √3x = 8√3 ⇒ x = 8cm
∴ Surface area of the cube = 6x² = 6 × 8 × 8 = 384 sq. cm