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Cubic Numbers & Patterns

Define perfect cubes algebraically and geometrically, exploring unit digit patterns and sums of consecutive odd numbers.

7 micro-lessons

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What is a Perfect Cube?

Defining cubes geometrically and algebraically.

Think of a cube you might see in geometry—a solid figure where all sides meet at right angles and are equal in length. In mathematics, a cubic number represents the volume of such a shape.

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Notation for Cubes

Formal notation and examples.

n^{3} = n \times n \times n

Just like whole numbers, we can cube fractions, decimals, and negative numbers.

Fractions

(\frac{4}{6})^{3} = \frac{4}{6} \times \frac{4}{6} \times \frac{4}{6} = \frac{64}{216}

Decimals

(13.08)^{3} = 13.08 \times 13.08 \times 13.08 = 2237.810112

Negatives

(- 6)^{3} = - 6 \times - 6 \times - 6 = - 216

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Patterns in Cubes

Unit digits and zero rules.

The Last Digits of Cubes

When you studied perfect squares, you learned they can only end in 0, 1, 4, 5, 6, or 9. Is there a similar rule for perfect cubes?

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Do You Know

Taxicab Numbers

Hardy-Ramanujan Number 1729.

$Visual learning concept$

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When mathematician G. H. Hardy visited Srinivasa Ramanujan in a hospital, he remarked that his taxicab number, 1729, was rather “dull”.

Ramanujan instantly replied that it was actually a very interesting number.

It is the smallest number that can be expressed as the sum of two cubes in two different ways. These are now known as Taxicab Numbers.
$1729 = 1^3 + 12^3 = 9^3 + 10^3$

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Cubes and Consecutive Odd Numbers

Summing blocks of odd numbers yields cubes.

Perfect cubes have a hidden mathematical relationship with consecutive odd numbers. Let's look at this fascinating pattern of addition.

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quiz

True or False: Cubes

Test conceptual rules of cubes.

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A student claims: "The cube of any odd number must be even." Is this statement true or false?

← previousEstimating Square Roots next →Finding Cube Roots

Do You Know

Taxicab Numbers

Hardy-Ramanujan Number 1729.

$Visual learning concept$

Click to zoom

When mathematician G. H. Hardy visited Srinivasa Ramanujan in a hospital, he remarked that his taxicab number, 1729, was rather “dull”.

Ramanujan instantly replied that it was actually a very interesting number.

It is the smallest number that can be expressed as the sum of two cubes in two different ways. These are now known as Taxicab Numbers.
$1729 = 1^3 + 12^3 = 9^3 + 10^3$

quiz

True or False: Cubes

Test conceptual rules of cubes.

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A student claims: "The cube of any odd number must be even." Is this statement true or false?