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Question

The volume of a solid cylinder is $55,440 \text{ cm}^3$ and its height is 40 cm. What is the total surface area of the solid cylinder?
(Use $\pi = \frac{22}{7}$)

The correct answer is
$8052 \text{ cm}^2$

Understanding the Cylinder Problem

The question asks us to find the total surface area (TSA) of a solid cylinder. We are given the volume (V) of the cylinder as $55,440 \text{ cm}^3$ and its height (h) as 40 cm. We are also told to use the value $\pi = \frac{22}{7}$.

Key Formulas for Cylinders

To solve this problem, we need two main formulas related to cylinders:

  • Volume of a Cylinder (V): $V = \pi r^2 h$, where $r$ is the radius and $h$ is the height.
  • Total Surface Area of a Cylinder (TSA): $TSA = 2\pi r (r+h)$, where $r$ is the radius and $h$ is the height.

We have the volume and height, so we can use the volume formula first to find the radius ($r$). Once we have the radius, we can use the TSA formula to calculate the total surface area.

Step-by-Step Calculation

Step 1: Finding the Radius (r)

We start with the formula for the volume of a cylinder: $V = \pi r^2 h$

Now, substitute the given values: $V = 55,440$, $h = 40$, and $\pi = \frac{22}{7}$. $55,440 = \frac{22}{7} \times r^2 \times 40$

To find $r^2$, we rearrange the equation: $r^2 = \frac{55,440 \times 7}{22 \times 40}$

Let's simplify the calculation: $r^2 = \frac{55,440}{880} \times 7$ First, divide 55,440 by 880: $ \frac{55440}{880} = \frac{5544}{88} = 63 $ So, the equation becomes: $r^2 = 63 \times 7$ $r^2 = 441$

Now, find the radius $r$ by taking the square root of 441: $r = \sqrt{441}$ $r = 21 \text{ cm}$ So, the radius of the cylinder is 21 cm.

Step 2: Calculating the Total Surface Area (TSA)

Now that we have the radius ($r = 21 \text{ cm}$) and the height ($h = 40 \text{ cm}$), we can calculate the total surface area using the formula: $TSA = 2\pi r (r+h)$

Substitute the values: $\pi = \frac{22}{7}$, $r = 21$, and $h = 40$. $TSA = 2 \times \frac{22}{7} \times 21 \times (21 + 40)$

First, simplify the term $2 \times \frac{22}{7} \times 21$: $2 \times 22 \times \frac{21}{7} = 2 \times 22 \times 3 = 132$

Next, calculate the term in the parenthesis: $(21 + 40) = 61$

Now, multiply these results together: $TSA = 132 \times 61$ Performing the multiplication: $132 \times 61 = 8052$

Therefore, the total surface area of the solid cylinder is $8052 \text{ cm}^2$.

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Important Questions from Mensuration 3D (Notes)

  1. A cylindrical rod has an outer curved surface area of \(7500 \text{ cm}^2\). If the length of the rod is 92 cm, then the outer radius (in cm) of the rod, rounded off to two places of decimal, is:
    \(\left(\text{Take } \pi = \frac{22}{7}\right)\)
  2. A number of 512 identical small spheres are cast from a sphere of radius 40 cm, with the total volume of the small spheres being equal to the volume of the larger sphere. The diameter (in cm) of each of the small spheres is:
  3. If the lateral surface area of a cylinder is 775.8 cm$^2$ and its height is 24 cm, then find its volume. (Use $\pi = 3.14$ and round off to two decimal places.)
  4. Find the Total surface area of the hemisphere (in $cm^2$) whose radius is 26cm and $\pi = 3.14$.
  5. Find the Total surface area of the hemisphere (in $cm^2$) whose radius is $48cm$ and $\pi = 3.14$.
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