- 638/996 - 630/998 + 645/986 + 653/999 - 670/1,007 + 637/1,021 = ? Adding Up Common (Ordinary) Fractions, Online Calculator. Addition Operation Explained Step by Step

Fractions' addition: - 638/996 - 630/998 + 645/986 + 653/999 - 670/1,007 + 637/1,021 = ?

Simplify the operation

Reduce (simplify) the fractions to their lowest terms equivalents:

  • To reduce a fraction to its lowest terms equivalent: divide the numerator and denominator by their greatest common factor, GCF.
  • * Why do we reduce (simplify) the fractions?
  • By reducing the values of the numerators and denominators of fractions, further calculations with these fractions become easier to do.
  • A fraction that was reduced (simplified) to the lowest terms is one with the smallest possible numerator and denominator, one that can no longer be reduced, and it is called an irreducible fraction.

* * *

The fraction: - 638/996

  • The prime factorizations of the numerator and denominator:
  • 638 = 2 × 11 × 29
  • 996 = 22 × 3 × 83
  • Multiply all the common prime factors: if there are repeating prime factors we only take them once, and only the ones having the lowest exponent (the lowest powers).
  • GCF (638; 996) = 2

- 638/996 = - (638 ÷ 2)/(996 ÷ 2) = - 319/498


  • Yet another method to simplify the fraction:

  • Without calculating GCF, factor the numerator and denominator and cross out all the common prime factors.
  • - 638/996 = - (2 × 11 × 29)/(22 × 3 × 83) = - ((2 × 11 × 29) ÷ 2)/((22 × 3 × 83) ÷ 2) = - 319/498


The fraction: - 630/998

  • 630 = 2 × 32 × 5 × 7
  • 998 = 2 × 499
  • GCF (630; 998) = 2

- 630/998 = - (630 ÷ 2)/(998 ÷ 2) = - 315/499


  • We could have simplified the fraction without calculating the GCF. Just factor the numerator and denominator and cross out the common prime factors.
  • - 630/998 = - (2 × 32 × 5 × 7)/(2 × 499) = - ((2 × 32 × 5 × 7) ÷ 2)/((2 × 499) ÷ 2) = - 315/499


The fraction: 645/986

645/986 is already reduced to the lowest terms.


  • The numerator and denominator have no common prime factors.
  • Their prime factorization:
  • 645 = 3 × 5 × 43
  • 986 = 2 × 17 × 29
  • GCF (3 × 5 × 43; 2 × 17 × 29) = 1

The fraction: 653/999

653/999 is already reduced to the lowest terms.


  • The numerator and denominator have no common prime factors.
  • Their prime factorization:
  • 653 is a prime number
  • 999 = 33 × 37
  • GCF (653; 33 × 37) = 1

The fraction: - 670/1,007

- 670/1,007 is already reduced to the lowest terms.


  • The numerator and denominator have no common prime factors.
  • Their prime factorization:
  • 670 = 2 × 5 × 67
  • 1,007 = 19 × 53
  • GCF (2 × 5 × 67; 19 × 53) = 1

The fraction: 637/1,021

637/1,021 is already reduced to the lowest terms.


  • The numerator and denominator have no common prime factors.
  • Their prime factorization:
  • 637 = 72 × 13
  • 1,021 is a prime number
  • GCF (72 × 13; 1,021) = 1


Rewrite the equivalent simplified operation:

- 638/996 - 630/998 + 645/986 + 653/999 - 670/1,007 + 637/1,021 =


- 319/498 - 315/499 + 645/986 + 653/999 - 670/1,007 + 637/1,021

Perform the operation of calculating the fractions.

To add or subtract fractions we need them to have equal denominators (the same common denominator).

  • To perform the operation of calculating the fractions we have to:
  • 1) find their common denominator
  • 2) then calculate the expanding number of each fraction
  • 3) then make their denominators the same by expanding the fractions to equivalent forms - which all have equal denominators (the same denominator)

  • * The common denominator is nothing else than the least common multiple (LCM) of the denominators of the fractions.
  • The LCM will be the common denominator of the fractions that we work with.

1) Find the common denominator
Calculate the LCM of the denominators:

The prime factorization of the denominators:


498 = 2 × 3 × 83


499 is a prime number


986 = 2 × 17 × 29


999 = 33 × 37


1,007 = 19 × 53


1,021 is a prime number


Multiply all the unique prime factors: if there are repeating prime factors we only take them once, and only the ones having the highest exponent (the highest powers).

LCM (498; 499; 986; 999; 1,007; 1,021) = 2 × 33 × 17 × 19 × 29 × 37 × 53 × 83 × 499 × 1,021 = 41,944,618,993,215,186



2) Calculate the expanding number of each fraction:

Divide the LCM by the denominator of each fraction.


- 319/498 ⟶ 41,944,618,993,215,186 ÷ 498 = (2 × 33 × 17 × 19 × 29 × 37 × 53 × 83 × 499 × 1,021) ÷ (2 × 3 × 83) = 84,226,142,556,657


- 315/499 ⟶ 41,944,618,993,215,186 ÷ 499 = (2 × 33 × 17 × 19 × 29 × 37 × 53 × 83 × 499 × 1,021) ÷ 499 = 84,057,352,691,814


645/986 ⟶ 41,944,618,993,215,186 ÷ 986 = (2 × 33 × 17 × 19 × 29 × 37 × 53 × 83 × 499 × 1,021) ÷ (2 × 17 × 29) = 42,540,181,534,701


653/999 ⟶ 41,944,618,993,215,186 ÷ 999 = (2 × 33 × 17 × 19 × 29 × 37 × 53 × 83 × 499 × 1,021) ÷ (33 × 37) = 41,986,605,598,814


- 670/1,007 ⟶ 41,944,618,993,215,186 ÷ 1,007 = (2 × 33 × 17 × 19 × 29 × 37 × 53 × 83 × 499 × 1,021) ÷ (19 × 53) = 41,653,047,659,598


637/1,021 ⟶ 41,944,618,993,215,186 ÷ 1,021 = (2 × 33 × 17 × 19 × 29 × 37 × 53 × 83 × 499 × 1,021) ÷ 1,021 = 41,081,899,111,866


3) Make fractions' denominators the same:

  • Expand each fraction: multiply both its numerator and denominator by its corresponding expanding number, calculated at the step 2, above. This way all the fractions will have the same denominator.
  • Then keep the common denominator and work only with the numerators of the fractions.

- 319/498 - 315/499 + 645/986 + 653/999 - 670/1,007 + 637/1,021 =


- (84,226,142,556,657 × 319)/(84,226,142,556,657 × 498) - (84,057,352,691,814 × 315)/(84,057,352,691,814 × 499) + (42,540,181,534,701 × 645)/(42,540,181,534,701 × 986) + (41,986,605,598,814 × 653)/(41,986,605,598,814 × 999) - (41,653,047,659,598 × 670)/(41,653,047,659,598 × 1,007) + (41,081,899,111,866 × 637)/(41,081,899,111,866 × 1,021) =


- 26,868,139,475,573,583/41,944,618,993,215,186 - 26,478,066,097,921,410/41,944,618,993,215,186 + 27,438,417,089,882,145/41,944,618,993,215,186 + 27,417,253,456,025,542/41,944,618,993,215,186 - 27,907,541,931,930,660/41,944,618,993,215,186 + 26,169,169,734,258,642/41,944,618,993,215,186 =


( - 26,868,139,475,573,583 - 26,478,066,097,921,410 + 27,438,417,089,882,145 + 27,417,253,456,025,542 - 27,907,541,931,930,660 + 26,169,169,734,258,642)/41,944,618,993,215,186 =


- 228,907,225,259,324/41,944,618,993,215,186


Reduce (simplify) the fraction to its lowest terms equivalent:

Calculate the greatest common factor, GCF,
of the numerator and denominator of the fraction:

  • The prime factorizations of the numerator and denominator:
  • 228,907,225,259,324 = 22 × 173 × 330,790,787,947
  • 41,944,618,993,215,186 = 24 × 1,069 × 2,851 × 860,164,171

Multiply all the common prime factors: if there are repeating prime factors we only take them once, and only the ones having the lowest exponent (the lowest powers).


GCF (228,907,225,259,324; 41,944,618,993,215,186) = GCF (22 × 173 × 330,790,787,947; 24 × 1,069 × 2,851 × 860,164,171) = 22

The fraction can be reduced (simplified):

Divide both the numerator and denominator by their greatest common factor, GCF.


- 228,907,225,259,324/41,944,618,993,215,186 =

- (228,907,225,259,324 ÷ 4)/(41,944,618,993,215,186 ÷ 41,944,618,993,215,186) =

- 57,226,806,314,831/10,486,154,748,303,796


We could have simplified the fraction without calculating the GCF. Just factor the numerator and denominator and cross out the common prime factors.


- 228,907,225,259,324/41,944,618,993,215,186 =


- (22 × 173 × 330,790,787,947)/(24 × 1,069 × 2,851 × 860,164,171) =


- ((22 × 173 × 330,790,787,947) ÷ 22)/((24 × 1,069 × 2,851 × 860,164,171) ÷ 22) =


- (173 × 330,790,787,947)/(22 × 1,069 × 2,851 × 860,164,171) =


- 57,226,806,314,831/10,486,154,748,303,796



Rewrite the equivalent simplified operation:

- 228,907,225,259,324/41,944,618,993,215,186 =


- 57,226,806,314,831/10,486,154,748,303,796


Rewrite the fraction

As a decimal number:

Simply divide the numerator by the denominator, without a remainder, as shown below:


- 57,226,806,314,831/10,486,154,748,303,796 =


- 57,226,806,314,831 ÷ 10,486,154,748,303,796 ≈


- 0.00545736809 ≈


- 0.01

As a percentage:

  • A percentage value p% is equal to the fraction: p/100, for any decimal number p. So, we need to change the form of the number calculated above, to show a denominator of 100.
  • To do that, multiply the number by the fraction 100/100.
  • The value of the fraction 100/100 = 1, so by multiplying the number by this fraction the result is not changing, only the form.

- 0.00545736809 =


- 0.00545736809 × 100/100 =


( - 0.00545736809 × 100)/100 =


- 0.545736809044/100


- 0.545736809044% ≈


- 0.55%



The final answer:
:: written in three ways ::

As a negative proper fraction:
(the numerator < the denominator)
- 638/996 - 630/998 + 645/986 + 653/999 - 670/1,007 + 637/1,021 = - 57,226,806,314,831/10,486,154,748,303,796

As a decimal number:
- 638/996 - 630/998 + 645/986 + 653/999 - 670/1,007 + 637/1,021 ≈ - 0.01

As a percentage:
- 638/996 - 630/998 + 645/986 + 653/999 - 670/1,007 + 637/1,021 ≈ - 0.55%

How are the numbers written: comma ',' used as a thousands separator; point '.' as a decimal separator; numbers rounded off to max. 12 decimals (if the case). The symbols used: '/' fraction bar; ÷ dividing; × multiplying; + plus (adding); - minus (subtracting); = equal; ≈ approximately equal.

Other similar operations:

How to add the common ordinary fractions:
641/1,005 + 639/1,005 + 653/992 - 655/1,005 + 672/1,013 + 645/1,027

Add common ordinary fractions, online calculator:

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