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Operations with decimal rational numbers


Addition and Subtraction

Addition

Consider the following addition:

1,28 + 2,6 + 0,038

Transforming into decimal fractions we have:

Practical method:

1º) We equate the number of decimal places, with the addition of zeros;
2º) We put comma under comma;
3º) We made the addition, placing the comma in the sum aligned with the others.

Examples:

1,28 + 2,6 + 0,03835,4 + 0,75 + 476,14 + 1,8 + 0,007

Subtraction

Consider the following subtraction:

3,97 - 2,013

Transforming into decimal fractions we have:

Practical method:

1º) We equate the number of decimal places, with the addition of zeros;
2º) We put comma under comma;
3º) We performed the subtraction, placing the comma in the difference, aligned with the others.

Examples:

3,97 - 2,01317,2 - 5,1469 - 0,987
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