All questions of Surface Area, Volume and Capacity (Cuboid, Cube and Cylinder) for Class 8 Exam
The curved surface area is calculated using the formula 2πrh. Substituting the values, Curved Surface Area = 2 × π × 3 cm × 12 cm = 226.08 cm².
Understanding Room Dimensions
The room has dimensions of 5 m (length) × 4 m (width) × 3 m (height). To find the total surface area while excluding the floor, we will calculate the areas of the four walls and the ceiling.
Calculating the Areas of Walls
1. Area of Two Longer Walls (Length × Height):
- Each wall's area = Length × Height = 5 m × 3 m = 15 m²
- Total for two walls = 2 × 15 m² = 30 m²
2. Area of Two Shorter Walls (Width × Height):
- Each wall's area = Width × Height = 4 m × 3 m = 12 m²
- Total for two walls = 2 × 12 m² = 24 m²
Calculating the Area of the Ceiling
3. Area of the Ceiling (Length × Width):
- Ceiling area = Length × Width = 5 m × 4 m = 20 m²
Summing Up the Areas
4. Total Surface Area Calculation:
- Total wall area = Area of longer walls + Area of shorter walls = 30 m² + 24 m² = 54 m²
- Adding the ceiling area = Total wall area + Ceiling area = 54 m² + 20 m² = 74 m²
However, since we need to exclude the floor, we only consider the walls and the ceiling:
Final Calculation
- Total area excluding the floor = 54 m² (walls) + 20 m² (ceiling) = 74 m²
Conclusion
The total surface area of the room, excluding the floor, is 54 m². Therefore, the correct answer is option 'C'.
The area of the walls is calculated as 2 × (Length + Width) × Height = 2 × (4 + 5) × 3 = 54 m².
Volume refers to the total space occupied by the solid material of the container, while capacity refers specifically to the internal volume available for holding liquids or gases.
The volume of a cuboid is calculated using the formula Volume = Length × Width × Height. This formula reflects the three dimensions of the cuboid, allowing us to determine the total space it occupies.
The total surface area is calculated by the formula 2(lb + bh + hl). Substituting gives 2(2 × 3 + 3 × 4 + 4 × 2) = 2(6 + 12 + 8) = 2(26) = 52 m².
The formula for volume is V = πr²h. Rearranging gives r = √(V/(πh)). Substituting the values, r = √(1050/(π × 15)) ≈ 7 cm.
1 cubic meter is equivalent to 1,000 liters. This equivalence is important in conversions for various applications, particularly in water storage and utility measurements.
The total surface area of a cylinder is given by the formula Total Surface Area = 2πrh + 2πr², which includes both the curved surface area and the areas of the two circular bases.
To find the internal volume, first calculate the internal dimensions: Length = 30 - 2(1) = 28 cm, Breadth = 20 - 2(1) = 18 cm, Height = 15 - 2(1) = 13 cm. Therefore, the internal volume = 28 × 18 × 13 = 6,072 cm³.
To find the internal dimensions, subtract twice the thickness from each external dimension: Length = 50 - 2(3) = 44 cm, Breadth = 40 - 2(3) = 34 cm, Height = 30 - 2(3) = 24 cm.
The volume of a cylinder is given by V = πr²h. Using π ≈ 3.14, V = 3.14 × (7 cm)² × 10 cm = 3.14 × 49 × 10 ≈ 1539.4 cm³, which rounds to approximately 1540 cm³.
The total surface area of a cube is calculated using the formula Total Surface Area = 6 × (Edge Length)². For a cube with an edge of 4 cm, the total surface area is 6 × (4 cm)² = 6 × 16 cm² = 96 cm².
Volume is generally expressed in cubic units, such as cubic centimeters (cm³) or cubic meters (m³). This measurement accounts for the three-dimensional space an object occupies.
The total surface area of a cube is given by 6a². Setting 6a² = 216 gives a² = 36, so a = 6 cm. Each edge of the cube is 6 cm long.
The volume of a cube is calculated using the formula Volume = a³, where 'a' is the length of one edge. This formula highlights the property of cubes where all sides are equal.
First, calculate the external volume: 12 × 10 × 8 = 960 cm³. Then, calculate the internal dimensions: 10 × 8 × 6 = 480 cm³. The volume of the material is 960 - 480 = 480 cm³.
Since 1 liter is equivalent to 1,000 cm³, a capacity of 2 liters equals 2 × 1,000 cm³ = 2,000 cm³. This conversion is crucial in various applications, including cooking and laboratory settings.
Let the dimensions be 2x, 3x, and 4x. The volume V = 2x × 3x × 4x = 24x³. Setting 24x³ = 120 gives x³ = 5, thus x = 1.71. The longest side = 4x = 6.86 cm, rounding gives approximately 8 cm.
The volume of the block is calculated as Volume = Length × Width × Height = 10 cm × 5 cm × 2 cm = 100 cm³.