Mathematics Grade 8 15 min

Volume of spheres

Volume of spheres

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Introduction & Learning Objectives

Learning Objectives Identify the key components of a sphere, including its radius and diameter. State the formula for the volume of a sphere. Substitute given values for radius or diameter into the volume formula. Calculate the volume of a sphere given its radius, using the correct units. Calculate the volume of a sphere given its diameter, using the correct units. Solve real-world problems involving the volume of spheres. Ever wondered how much air is inside a basketball, or how much ice cream fits into a perfectly round scoop? 🏀🍦 Today, we'll learn how to measure the space inside these amazing 3D shapes! In this tutorial, you will learn how to calculate the volume of a sphere. Understanding this concept is crucial for solving problems involving three-dimensional ob...
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Key Concepts & Vocabulary

TermDefinitionExample SphereA perfectly round three-dimensional object, where every point on its surface is equidistant from its center.A basketball, a globe, a marble. Radius (r)The distance from the center of a sphere to any point on its surface.If a sphere has a diameter of 10 cm, its radius is 5 cm. Diameter (d)The distance across a sphere passing through its center. It is twice the radius.If a sphere has a radius of 7 inches, its diameter is 14 inches. Volume (V)The amount of three-dimensional space occupied by an object. For a sphere, it's how much 'stuff' can fit inside it.A sphere with a volume of 300 cubic centimeters can hold 300 cm³ of water. Pi (π)A mathematical constant representing the ratio of a circle's circumference to its diameter, approximately 3.141...
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Core Formulas

Volume of a Sphere Formula $$V = \frac{4}{3}\pi r^3$$ This formula is used to calculate the volume (V) of any sphere, where 'r' is the radius of the sphere and 'π' (pi) is a mathematical constant (approximately 3.14). Radius from Diameter $$r = \frac{d}{2}$$ If you are given the diameter (d) of a sphere, you must first find the radius (r) by dividing the diameter by 2 before using the volume formula.

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Sample Practice Questions

Challenging
A sphere is perfectly inscribed inside a cube with a side length of 8 cm, meaning the sphere touches all six faces of the cube. What is the volume of the sphere? Use π ≈ 3.14.
A.2143.57 cm³
B.267.95 cm³
C.512.00 cm³
D.1071.79 cm³
Challenging
The volume of a sphere is exactly 288π cubic units. What is its radius?
A.6 units
B.8 units
C.12 units
D.216 units
Challenging
If the radius of a sphere is tripled, what happens to its volume?
A.It increases by a factor of 3.
B.It increases by a factor of 6.
C.It increases by a factor of 9.
D.It increases by a factor of 27.

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