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Question

The surface area (in cm²) of a sphere of radius 14 cm is: Take π = 22/7

The correct answer is
2464

Understanding Sphere Surface Area Calculation

The question asks for the surface area of a sphere given its radius and the value of π.

Given Information:

  • Radius of the sphere, $r = 14$ cm
  • Value of π, $ \pi = \frac{22}{7} $

Formula Needed:

The formula for the surface area (A) of a sphere is:

$$A = 4 \pi r^2$$

Step-by-Step Calculation

  1. Substitute the given values into the formula:

    $$A = 4 \times \frac{22}{7} \times (14 \text{ cm})^2$$

  2. Expand the radius squared term:

    $$A = 4 \times \frac{22}{7} \times (14 \text{ cm} \times 14 \text{ cm})$$

  3. Simplify the expression by canceling out the common factor of 7:

    $$A = 4 \times 22 \times \left(\frac{14}{7}\right) \times 14 \text{ cm}^2$$

    $$A = 4 \times 22 \times 2 \times 14 \text{ cm}^2$$

  4. Perform the multiplication:

    First, multiply 4 by 22:

    $$4 \times 22 = 88$$

    Then, multiply the result by 2:

    $$88 \times 2 = 176$$

    Finally, multiply this by 14:

    $$176 \times 14$$

    To calculate $176 \times 14$:

    $$176 \times 10 = 1760$$

    $$176 \times 4 = 704$$

    $$1760 + 704 = 2464$$

    Therefore, the surface area is:

    $$A = 2464 \text{ cm}^2$$

Result Verification

The calculated surface area is 2464 cm². This matches option 4.

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Important Questions from Mensuration

  1. The areas of three adjacent faces of a cuboidal tank are 3 m 2, 12 m 2 and 16 m 2. the capacity of the tank, in litres, is:

  2. Volume of a cuboid is 4800 cm 3. If the height of this cuboid is 20 cm, then what will be the area of the base of cuboid ?

  3. Two similar cubes have heights of 8 cm and 12 cm, respectively. If the capacity of the smaller cube is 80 cm 3, what is the capacity of the bigger cube (in cm 3)?

  4. Three circles of radius 7 cm are kept touching each other. The string is tightly tied around these three circles. What is the length of the string?

  5. Three circles of radius 6 cm are kept touching each other. The string is tightly tied around these three circles. What is the length of the string?

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