Basic property of a fraction

In this publication, we will consider the main property of an ordinary fraction, studied in the school algebra curriculum in grades 6-8. We will also analyze examples of solving problems for a better understanding of the theoretical material.

Content

Formulation of the basic property of a fraction

If the numerator and denominator are multiplied (or divided) by the same natural number, then the value of the fraction will remain unchanged.

Those. 
2/5

=

2⋅3/5⋅3

=

6/15

Examples of tasks

Task 1

Choose among the listed fractions those that are equal to the fraction 
4/9

:

5/11

2/10

20/45

2/3

6/14

.

 

Solution

Among the listed fractions 
4/9

 are equal 

20/45

 и 

2/3

 , because:

 

20/45

=

4⋅5/9⋅5

, that is, the numerator and denominator are multiplied by the number 5.

 

2/3

=

4:2/9:2

, i.e. numerator and denominator divided by 2.

 

Task 2

Determine at what value x, fraction 
x/7

 equals a fraction 

3/21

.

 

Solution

According to the main property discussed above, the fraction 
x/7

 may equal 

3/21

 only if its numerator and denominator are multiplied/divided by the same number.

 

We know the denominators of both fractions, so we can easily find the missing factor (or divisor) by dividing one value by another: 21: 7 = 3.

 

Therefore, the quotient of dividing the numerators must also be equal to three:

In 3: x = 3

x = 1

 

Answer: 
1/7

.

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