Question
Find the surface area of a sphere whose diameter is equal to 28 cm.
The correct answer is
784π cm²
To find the surface area of a sphere whose diameter is 28 cm, we use the formula for the surface area of a sphere, which is \(4\pi r^2\), where \(r\) is the radius of the sphere.
First, calculate the radius by dividing the diameter by 2: \(r = \frac{28\text{ cm}}{2} = 14\text{ cm}\).
Now, substitute the radius into the formula:
\( \text{Surface Area} = 4\pi (14\text{ cm})^2 \)
Simplify this expression:
\( = 4\pi \times 196\text{ cm}^2 \)
\( = 784\pi\text{ cm}^2 \)
Thus, the surface area of the sphere is \(784\pi\text{ cm}^2\).
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Important Questions from Mensuration
- The volume of a wall that is 5 times as high as it is broad and 8 times as long as it is high is 12.8 cubic meters. Find the breadth of the wall.
- If the radius of a sphere is increased by 2 cm, then its surface area increases by 704 cm\(^2\). Using \(\pi = \frac{22}{7}\), find the radius of the sphere after the increase.
- What is the perimeter of an equilateral triangle with side 13 cm?
- The perimeter of a square is 76 m. Its area (in $m^2$) is:
- A cylindrical rod has an outer curved surface area of 1800 cm$^2$. If the length of the rod is 52 cm, then the outer radius (in cm) of the rod, correct to two places of decimal, is:
Take $\pi = \frac{22}{7}$
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