Math Problem Statement

What is the exact volume of the cone?

Solution

This problem involves finding the volume of a cone, which is calculated using the formula:

V=13πr2hV = \frac{1}{3} \pi r^2 h

From the diagram:

  • The slant height is 13cm13 \, \text{cm}.
  • The height of the cone is h=12cmh = 12 \, \text{cm}.
  • We need to find the radius rr using the Pythagorean theorem, since the slant height, height, and radius form a right triangle.

Step 1: Apply the Pythagorean theorem

r2+h2=(slant height)2r^2 + h^2 = (\text{slant height})^2 Substituting the values: r2+122=132r^2 + 12^2 = 13^2 r2+144=169r^2 + 144 = 169 r2=169144=25r^2 = 169 - 144 = 25 r=25=5cmr = \sqrt{25} = 5 \, \text{cm}

Step 2: Calculate the volume

Now that we know r=5cmr = 5 \, \text{cm} and h=12cmh = 12 \, \text{cm}, substitute into the cone volume formula: V=13πr2hV = \frac{1}{3} \pi r^2 h V=13π(52)(12)V = \frac{1}{3} \pi (5^2)(12) V=13π(25)(12)V = \frac{1}{3} \pi (25)(12) V=13π(300)V = \frac{1}{3} \pi (300) V=100πcm3V = 100 \pi \, \text{cm}^3

Final Answer:

The exact volume of the cone is: 100πcm3\boxed{100 \pi \, \text{cm}^3}

Let me know if you need further clarification!


Questions for Expansion:

  1. What would the volume be if the slant height was increased to 15 cm while keeping the height constant?
  2. How does the formula for the volume of a cone differ from that of a cylinder?
  3. Can we derive the formula for the volume of a cone using integration?
  4. How would the volume change if the radius were doubled but the height remained the same?
  5. How do we calculate the surface area of this cone?

Tip:

Always confirm the radius using the Pythagorean theorem when given the slant height and height of a cone.

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Math Problem Analysis

Mathematical Concepts

Geometry
Cone Volume
Pythagorean Theorem

Formulas

Volume of a cone: V = (1/3)πr²h
Pythagorean Theorem: a² + b² = c²

Theorems

Pythagorean Theorem

Suitable Grade Level

Grades 8-10