Multiplication of an ordinary fraction by a decimal: rule, examples

In this publication, we will consider how an ordinary (simple) fraction can be multiplied by a decimal. We will also analyze examples to consolidate the theoretical material.

Content

Product of common and decimal fractions

To multiply an ordinary fraction by a decimal (and vice versa, because the result does not change from a permutation of the factors), it is necessary to represent one of the fractions as another.

Notes:

1. Infinite decimals are required first, i.e. leave a finite number of digits after the decimal point.

2. Mixed ordinary fractions must first be converted to.

Examples

Example 1

Let’s find the product of a fraction 
3/20

 and 2,19.

 

Solution 1

Let’s translate:

3/20

=

3⋅5/20⋅5

=

15/100

= 0,15

 

Now let’s execute:

0,15 ⋅ 2,19 = 0,3285.

Solution 2

Let’s transform:

= 2,19 2
19/100

=

2 ⋅ 100 + 19/100

=

219/100

 

It remains only to find:

219/100

3/20

=

219⋅3/100⋅20

=

657/2000

 

Example 2

Multiply 6,24 by fraction 2
4/9

.

 

Solution

Convert the given mixed fraction to an improper one:

2
4/9

=

2 ⋅ 9 + 4/9

=

22/9

 

Next, we have a choice: either we translate the decimal fraction into an ordinary one, or vice versa. Let’s choose the first option.

= 6,24 6
24/100

=

6 ⋅ 100 + 24/100

=

624/100

 

Now we divide one simple fraction by another:

624/100

:

22/9

=

624/100

9/22

=

624⋅9/100⋅22

=

5616/2200

= 2

1216/2200

= 2

152/275

≈ 2,5528

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