📘 Concept & Theory Concept Used ›
A cone is a three-dimensional solid having a circular base and a curved surface meeting at a single point called the vertex.
The curved surface area of a cone represents the area covered only by the curved portion of the cone, excluding the circular base.
The formula for curved surface area of a cone is:
\[\small \text{Curved Surface Area of Cone} = \pi r l \]
where,
- \[\small r = \text{radius of the base} \]
- \[\small l = \text{slant height of the cone} \]
- \[\small \pi = \frac{22}{7} \] (used when numerical values are convenient)
🗺️ Solution Roadmap Step-by-step Plan ›
Find the radius using the given diameter.
Use the formula \[\small \pi r l \] for curved surface area.
Substitute the values carefully.
Simplify step by step to obtain the final answer.
📊 Graph / Figure Graph / Figure ›
✏️ Solution Complete Solution ›
- Diameter of the base of the cone is given as:\[\small d = 10.5~\text{cm}\]
- Radius is half of the diameter.\[\small r = \frac{d}{2}\]
- Substituting the value of diameter:\[\small \begin{aligned}r &= \frac{10.5}{2}\\r &= 5.25~\text{cm}\end{aligned}\]
- Slant height of the cone is given as:\[\small l = 10~\text{cm}\]
- Formula for curved surface area of a cone:\[\small \text{Curved Surface Area} = \pi r l\]
- Substituting the known values:\[\small = \frac{22}{7} \times 5.25 \times 10\]
- Convert decimal into multiplication form for easy simplification:\[\small 5.25 = \frac{525}{100}\]
- Therefore,\[\small = \frac{22}{7} \times \frac{525}{100} \times 10\]
- Simplifying\[\small \begin{aligned}&= \frac{22 \times 525 \times 10}{7 \times 100}\\ &= \frac{22 \times 75 \times 10}{100}\\ &= \frac{16500}{100}\\ &= 165\end{aligned}\]
💡 Answer Final Answer ›
🎯 Exam Significance Exam Significance ›
- This question strengthens the understanding of the formula for curved surface area of a cone.
- Questions based on surface areas are frequently asked in school examinations, unit tests, and board examinations.
- Competitive examinations often test direct formula application along with correct unit handling and simplification.
- It develops accuracy in substituting numerical values into mensuration formulas.
- Understanding such basic problems is essential before solving advanced problems involving combinations of solids.
🔑 Key Takeaways Key Takeaways ›
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Radius is always half of the diameter.
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Curved surface area of a cone is calculated using: \[\small \pi r l \]
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Slant height is used in curved surface area calculations, not vertical height.
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Proper simplification step by step reduces calculation mistakes.
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Final answers for surface area must be written in square units.