Fraction

Pronunciation: /ˈfræk ʃən/ ?

A fraction is an expression divided by an expression.[1] Examples of fractions are:

2/5

9/4

(x+3)/(x-2)
The expression on the top is called the numerator and the expression on the bottom is called the denominator.

numerator/denominator

Fractions whose values are greater than one are sometimes called improper fractions. Improper fractions are often easier to use than mixed numbers, especially when using computers.

A whole number followed by a fraction is called a mixed number. Two examples of mixed numbers are:

3 5/8

1 2/7

A complex fraction is a fraction with another fraction in the numerator and/or denominator:

(1+3/4)/2.

Operations on Fractions

For a complete list of rules for operations on fractions, see Fraction Rules.

OperationDescriptionExample
AdditionTo add 2 fractions:
  1. Find the least common denominator
  2. Convert each fraction to the least common denominator.
  3. Add the numerators, copy the common denominator
  4. Reduce the fraction, if needed.
5/6+2/10 = 25/30+6/30=(25+6)/30=31/30
SubtractionTo subtract 2 fractions:
  1. Find the common denominator
  2. Convert each fraction to the common denominator.
  3. Subtract the numerators, copy the common denominator
  4. Reduce the fraction, if needed.
5/6-2/10 = 25/30-6/30=(25-6)/30=19/30
MultiplicationTo multiply 2 fractions:
  1. Multiply the numerators.
  2. Multiply the denominators
  3. Reduce the fraction, if needed.
3/4*2/3=(3*2)/(4*3)=6/12=1/2.
DivisionTo divide 2 fraction: Multiply the first fraction by the reciprocal of the second fraction.(3/7)/(3/4)=(3/7)*(4/3)=12/21=7/4.
Least common denominatorTo find the least common denominator of two fractions:
  1. Find the prime factors of both fractions.
  2. Take the product of the prime factors, making sure each factor is multiplied once.
  3. The product is the least common denominator.
5/6 and 3/8. 6=2*3, 8=2*2*2,lcd(6,8)=2*2*2*3=24
Reduce a fractionTo reduce a fraction:
  1. Find the prime factors of both the numerator and the denominator.
  2. Cancel common factors.
  3. Multiply the remaining factors.
4/12=(2*2)/(2*2*3)=1/3

How to convert a mixed number to a fraction.

Original
Expression

Operation

Calculation

Description
12 3/5noneMixed number to convert.
22 3/52*5=10Multiply the whole number by the denominator. The product is 10.
32 3/510+3=13Add the product and the numerator. The sum is 13.
42 3/513/5Use the sum as the numerator and copy the denominator from the fraction.

Why this works:

2 3/5 represented as 13/5
Figure 1: Representation of converting 2 3/5 to 13/5.

How to convert a fraction to a mixed number.

StepOriginal
Expression
OperationDescription
123/7noneFraction to convert.
223/723/7 = 3 r 2Divide 23 by 7. This gives three wholes and a remainder of 2/7.
323/73 2/7Make the mixed number.

Why this works:

Representation of converting 23/7 to 3 2/7.
Figure 2: Representation of converting 23/7 to 3 2/7

References

  1. fraction. http://wordnet.princeton.edu/. WordNet. Princeton University. (Accessed: 2011-01-08). http://wordnetweb.princeton.edu/perl/webwn?s=fraction&sub=Search+WordNet&o2=&o0=1&o7=&o5=&o1=1&o6=&o4=&o3=&h=.
  2. Fine, Henry B., Ph. D.. Number-System of Algebra Treated Theoretically and Historically, 2nd ed., pp 12-15. D. C. Heath & Co., Boston, U.S.A., 1907. (Accessed: 2009-12-19). http://www.archive.org/stream/thenumbersystemo17920gut/17920-pdf#page/n21/mode/1up/search/fraction.
  3. Oberg, Erik. Arithmetic Simplified, pp 21-31. Industrial Press, 1914. (Accessed: 2010-01-22). http://www.archive.org/stream/arithmeticsimpli00oberrich#page/21/mode/1up/search/fraction.
  4. Oberg, Erik. Elementary Algebra, pg 23. Industrial Press, 1914. (Accessed: 2010-01-22). http://www.archive.org/stream/elementaryalgebr00oberrich#page/n26/mode/1up/search/fraction.
  5. Bettinger, Alvin K. and Englund, John A.. Algebra and Trigonometry, pp 9-11. International Textbook Company, January 1963. (Accessed: 2010-01-12). http://www.archive.org/stream/algebraandtrigon033520mbp#page/n18/mode/1up.

Printed Resources

Cite this article as:


Fraction. 2009-12-19. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/f/fraction.html.

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Revision History


2009-12-19: Added "References" (McAdams, David.)
2008-12-29: Changed 'complex fraction' from keyword to vocabulary link (McAdams, David.)
2008-11-28: Added section 'Complex Fractions' (McAdams, David.)
2008-11-26: Changed equations to images (McAdams, David.)
2008-09-16: Added text describing numerator and denominator, changed some expressions to hot_eqn (McAdams, David.)
2007-10-19: Clarified examples in How To section (McAdams, David.)
2007-09-23: Removed alert (McAdams, David.)
2007-08-20: Add this revision history (McAdams, David.)
2007-08-08: Initial version (McAdams, David.)

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