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Question

If the slant height of a cone is 60 cm and the radius of its base is 21 cm, then find its curved surface area. (use π = \({22 \ {} \over 7}\))

This question was previously asked in
SSC CGL 2023 (Tier-II) Paper 1 Previous Year Paper (26-Oct-2023) (Shift-1)
The correct answer is

3960 cm2

Calculating the Curved Surface Area of a Cone

Let's find the curved surface area of a cone using the given dimensions. We are provided with the slant height and the radius of the base.

The formula for the curved surface area (CSA) of a cone is:

CSA = πrl

Where:

  • r is the radius of the base
  • l is the slant height of the cone
  • π is the mathematical constant pi

In this problem, we are given:

  • Slant height, l = 60 cm
  • Radius of the base, r = 21 cm
  • We need to use π = ${22 \over 7}$

Now, let's substitute these values into the curved surface area formula:

CSA = ${22 \over 7} \times 21 \times 60$

We can simplify the calculation:

CSA = ${22 \times (21 \over 7) \times 60}$

CSA = ${22 \times 3 \times 60}$

First, calculate $22 \times 3$:

$22 \times 3 = 66$

Now, multiply the result by 60:

CSA = ${66 \times 60}$

CSA = $3960$

So, the curved surface area of the cone is 3960 cm2.

Cone Curved Surface Area Calculation Steps

Here are the steps we followed to calculate the curved surface area:

  1. Identify the given values for the radius (r) and slant height (l).
  2. Recall or find the formula for the curved surface area of a cone: CSA = πrl.
  3. Substitute the given values of r, l, and the specified value of π into the formula.
  4. Perform the necessary multiplication and division to calculate the CSA.
  5. State the final answer with the correct units (cm2).

Revision Table: Cone Formulas

Here is a quick summary of important formulas related to cones:

Formula Description Variables
Curved Surface Area (CSA) Area of the slanted surface πrl
Total Surface Area (TSA) Area of curved surface + Area of base πr(r + l)
Volume (V) Space occupied by the cone ${1 \over 3}\pi r^2h$
Slant Height (l) Relationship between height, radius, and slant height (Pythagorean theorem) $\sqrt{r^2 + h^2}$

Additional Information: Understanding Cone Dimensions

When working with cone problems, it's helpful to understand the different dimensions:

  • Radius (r): The distance from the center of the circular base to any point on its edge.
  • Height (h): The perpendicular distance from the apex (tip) of the cone to the center of the base.
  • Slant Height (l): The distance from the apex of the cone to any point on the circumference of the base. This is the length along the "slope" of the cone.

The height, radius, and slant height form a right-angled triangle, where the slant height is the hypotenuse. This relationship allows us to find one dimension if the other two are known, often using the Pythagorean theorem ($l^2 = r^2 + h^2$). In this specific problem, we only needed the radius and slant height for the curved surface area calculation.

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Similar Questions

  1. If the total surface area of a cube is 24 sq.units, then what is the volume of the cube?

  2. The volume of a cone is 73920 cm3. If the height of the cone is 160 cm, then find the diameter of its base.

  3. Ranu carries water to school in a cylindrical flask with diameter 12 cm and height 21 cm. Determine the amount of water that she can carry in the flask. (Use π = \(\frac{22}{7}\))

  4. The volume of a cone with height equal to radius, and slant height 5 cm is :

  5. What is the whole surface area of a cone of base radius 6 cm and height 8 cm?

  6. What is the volume of a cube if the perimeter of one face of the cube is 40 cm?

  7. A spherical ball of lead, 3 cm in diameter, is melted and recast into three spherical balls. The diameters of two of these balls are \(\frac{3}{2}\) cm and 2 cm, respectively. Find the diameter of the third ball.  

  8. A conical tent of height 10 m and base diameter 48 m was erected by a company in a park. Find the curved surface area of the tent (In m2).

  9. If the surface area of a cube is 5046 cm2, then the volume of the cube is:

  10. The volume of a cuboid is twice that of a cube. If the dimensions of the cuboid are (8 m × 8 m ×16 m), the total surface area of the cube is: 


Important Questions from Solid Figures

  1. The area of the floor of a cubical room is 192 m 2. The length of the longest rod that can be kept in that room is :

  2. A solid metallic rectangular block of dimensions 112 cm × 44 cm × 25 cm is melted and recast into a cylinder of radius 35 cm. The curved surface area (in cm 2) of the cylinder is: (Take π = 22/7)

  3. If the volume of a cube is 175616 cm 3, what is its side?

  4. The volume of a right circular cone is 1232 cm 3. If the height of the cone is 24 cm, then what will be the radius of its base?

  5. A right triangle contains the right angle between the sides 5 cm and 7 cm. A cone is generated by revolving about the side 5 cm. The volume of this cone is:

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