How To Completely Reduce (Simplify) the Fraction 21/7 to the Lowest Terms, Its Simplest Equivalent Form, Irreducible, With the Smallest Possible Numerator and Denominator (Prime to Each Other)? Write the Result as an Improper Fraction, as an Integer and as a Percentage

Reduce (simplify) the fraction: 21/7

To completely reduce (simplify) a fraction to its lowest terms, divide the numerator and the denominator of the fraction by their greatest (highest) common factor (divisor), gcf (hcf, gcd)

To calculate the greatest (highest) common factor (divisor), gcf (hcf, gcd), we perform the prime factorization of the two numbers.


The prime factorization of the two numbers:

The prime factorization of a number: finding the prime numbers that multiply together to make that number.


21 = 3 × 7
21 is not a prime number but a composite one.

7 is a prime number and cannot be broken down into other prime factors.


* The natural numbers that are only divisible by 1 and themselves are called prime numbers. A prime number has exactly two factors: 1 and itself.

* A composite number is a natural number that has at least one other factor than 1 and itself.



Calculate the greatest (highest) common factor (divisor), gcf (hcf, gcd):

Multiply all the common prime factors, taken by their smallest exponents (powers).

gcf, hcf, gcd (21; 7) = 7



Divide the numerator and the denominator of the fraction by their greatest (highest) common factor (divisor), gcf (hcf, gcd).

21/7 =


(3 × 7)/7 =


((3 × 7) ÷ 7) / (7 ÷ 7) =


3/1 =


(If the denominator is 1, it can be omitted)
3

The fraction is now completely reduced (simplified) to its lowest terms.

A fraction that is completely reduced (simplified) to its lowest terms (to its basic representation, to its simplest form) has the smallest possible numerator and denominator.


A fully reduced fraction is called an irreducible fraction and its numerator and denominator are coprime numbers.

3 = 3/1 is an improper fraction.

An improper fraction: the numerator is greater than or equal to the denominator.

Rewrite the result.

As an improper fraction
(the denominator = 1):

3 = 3/1


As a percentage:

Multiply the fraction's value by the fraction 100/100


100/100 = 100 ÷ 100 = 100% = 1

Multiply a number by the fraction 100/100,
... and its value will not change, only the form.


3 =


3 × 100/100 =


(3 × 100)/100 =


300/100 =


300%


The final answer:
:: Written in three ways ::

As an improper fraction:
21/7 = 3/1

As an integer:
21/7 = 3

As a percentage:
21/7 = 300%

Online Calculator: Completely reduce (simplify) fraction to the lowest terms

To fully reduce (simplify) fractions to the lowest terms:

Divide the numerator and denominator of the fraction by their greatest (highest) common factor (divisor), gcf (hcf, gcd).

Result written as a proper or an improper fraction, as a mixed number, as a decimal or an integer and as a percentage.

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Tutoring: simplifying fractions - reducing them to the lowest terms

Steps to simplify a fraction, to reduce it to its lowest terms:

  • A fraction fully simplified, a fraction reduced to its lowest terms is a fraction that can no longer be simplified, it has been reduced to its simplest equivalent fraction, the one having the smallest numerator and denominator possible - prime to each other.
  • 1) Run the prime factorization of both the numerator and the denominator of the fraction.
  • 2) Calculate the greatest common factor, GCF (or the greatest common divisor, GCD) of the fraction's numerator and denominator.
  • 3) Divide both the numerator and the denominator of the fraction by their greatest common factor, GCF (GCD).
  • The fraction thus obtained is called a reduced fraction or a fraction simplified to its lowest terms.
  • A fraction reduced to its lowest terms may no longer be reduced and it is called an irreducible fraction.

Example: reduce the fraction 315/1,155 as much as possible, simplify it to the lowest terms.

  • 1) Run the prime factorization of both the numerator and the denominator of the fraction.

  • The numerator of the fraction is 315, its breaking down into prime factors is:
    315 = 3 × 3 × 5 × 7 = 32 × 5 × 7
  • The denominator of the fraction is 1,155, its breaking down into prime factors is:
    1,155 = 3 × 5 × 7 × 11.
  • 2) Calculate the greatest common factor, GCF (or the greatest common divisor, GCD) of the fraction's numerator and denominator.

  • The greatest common factor, gcf (315; 1,155), is calculated by multiplying all the common prime factors of the numerator and the denominator, taken by their lowest powers (their lowest exponents):
  • GCF (315; 1,155) = (32 × 5 × 7; 3 × 5 × 7 × 11) = 3 × 5 × 7 = 105
  • 3) Divide both the numerator and the denominator of the fraction by their greatest common factor, GCF (GCD).

  • The numerator and denominator of the fraction are divided by their greatest common factor, GCF:
  • 315/1,155 =
    (32 × 5 × 7)/(3 × 5 × 7 × 11) =
    ((32 × 5 × 7) ÷ (3 × 5 × 7)) / ((3 × 5 × 7 × 11) ÷ (3 × 5 × 7)) =
    3/11
  • The fraction thus obtained is called a fraction reduced to the lowest terms.

Why reducing (simplifying) fractions to lower terms?

  • When running operations with fractions we are often required to bring them to the same denominator, for example when adding, subtracting or comparing.
  • Sometimes both the numerators and the denominators of those fractions are large numbers and doing calculations with such numbers could be difficult.
  • By reducing (simplifying) a fraction, both its numerator and denominator are reduced to smaller values, much easier to work with, which will decrease the overall effort of working with that fraction.

Read the entire article ⇒ Completely reduce (simplify) fractions to the lowest terms: Steps and Examples