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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. A solid cube is painted yellow, blue and black such that opposite faces are of same colour. The cube is then cut into 36 cubes of two different sizes such that 32 cubes are small and the other four cubes are Big. None of the faces of the bigger cubes is painted blue. How many cubes have only one face painted?

  2. A and B are two heavy steel blocks. If B is placed on the top of A, the weight increases by 60%. How much weight will reduce with respect to the total weight of A and B, if B is removed from the top of A?

  3. A gardener increased the area of his rectangular garden by increasing its length by 40% and decreasing its width by 20%. The area of the new garden

  4. A village having a population of 4000 requires 150 liters of water per head per day. It has a tank measuring 20 m x 15 m x 6 m. The water of this tank will last for

  5. The centroid of an equilateral triangle ABC is G. If AB is 6 cms, the length of AG is

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