Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
A cube of a number is obtained by multiplying the number by itself three times. Geometrically, if you have a solid cube with side length , its volume is represented by . For example, a cube with side units consists of unit cubes.
A natural number is called a perfect cube if it is the cube of some natural number. In terms of prime factorization, a number is a perfect cube only if each prime factor appears in groups of three (triplets). For instance, , which can be grouped as .
The units digit of a cube follows a specific pattern based on the units digit of the number: Numbers ending in have cubes ending in the same digits. However, numbers ending in have cubes ending in (and vice versa), and numbers ending in have cubes ending in (and vice versa).
The cube of an even number is always even, and the cube of an odd number is always odd. For example, (even) and (odd).
Cubes can be expressed as the sum of consecutive odd numbers. , , , and so on. To find , you sum consecutive odd numbers following the ones used for .
If a number ends with zeros, its cube ends with zeros. For example, (1 zero) has a cube of (3 zeros), and (2 zeros) has a cube of (6 zeros). This visualizes how the volume expands cubically in all three dimensions.
Cube root is the inverse operation of finding a cube. If , then the cube root of , denoted as , is . For example, since , then .
📐Formulae
💡Examples
Problem 1:
Determine if is a perfect cube. If not, find the smallest natural number by which must be multiplied so that the product is a perfect cube.
Solution:
Step 1: Find the prime factorization of . Step 2: Group the factors into triplets. Step 3: Identify the missing factor. The prime factor does not appear in a triplet (it only appears twice). Step 4: To make it a triplet, we need one more . Required number = . New product = , which is .
Explanation:
To be a perfect cube, every prime factor must occur in a group of three. Since occurred only twice, multiplying by completes the triplet.
Problem 2:
Find the cube root of using prime factorization.
Solution:
Step 1: Perform prime factorization of . So, Step 2: Take one factor from each triplet to find the cube root. .
Explanation:
The cube root is found by grouping prime factors into triplets and selecting one representative from each group to multiply together.