Skill: Add fractions with unlike denominators

Explanation and Free Practice Resources

Adding fractions with unlike denominators requires recognizing that the fractions must be expressed in equivalent forms with a common denominator, often the least common multiple, before combining their numerators; the result is then simplified and interpreted as a fraction or mixed number. The reasoning applies to numerical positive and negative fractions and reinforces equivalence, magnitude, and the meaning of a common unit, but does not extend to algebraic rational expressions, symbolic denominators, or more advanced generalizations.

Detailed Explanation: Add fractions with unlike denominators

To add fractions with unlike denominators, first rewrite them with a common denominator. Then add the numerators and simplify the result.

Example:

23+58\frac{2}{3}+\frac{5}{8}

The denominators are 33 and 88. Their least common multiple is 2424, so use 2424 as the common denominator.

Rewrite each fraction:

23=2×83×8=1624\frac{2}{3}=\frac{2\times 8}{3\times 8}=\frac{16}{24} 58=5×38×3=1524\frac{5}{8}=\frac{5\times 3}{8\times 3}=\frac{15}{24}

Now the fractions have the same-sized parts, so add the numerators:

1624+1524=3124\frac{16}{24}+\frac{15}{24}=\frac{31}{24}

The answer is an improper fraction. Convert it to a mixed number:

3124=1724\frac{31}{24}=1\frac{7}{24}

Therefore,

23+58=1724\boxed{\frac{2}{3}+\frac{5}{8}=1\frac{7}{24}}

Remember: find a common denominator, make equivalent fractions, add the numerators, and simplify or convert to a mixed number if needed.

Learn by doing: Add fractions with unlike denominators

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Fraction Addition - Basic (Simplifying Answers) - Two Changed Denominators


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