Example

Adding 712+1115\frac{7}{12} + \frac{11}{15}

Add two fractions with unlike denominators by first determining their least common denominator (LCD):

712+1115\frac{7}{12} + \frac{11}{15}

Step 1 — Find the LCD and rewrite: Factor the denominators: 12=22312 = 2 \cdot 2 \cdot 3 and 15=3515 = 3 \cdot 5. The LCD is 2235=602 \cdot 2 \cdot 3 \cdot 5 = 60. Multiply the numerator and denominator of the first fraction by 55 and the second fraction by 44 to convert them to equivalent fractions:

75125+114154=3560+4460\frac{7 \cdot 5}{12 \cdot 5} + \frac{11 \cdot 4}{15 \cdot 4} = \frac{35}{60} + \frac{44}{60}

Step 2 — Add: Combine the numerators over the common denominator:

35+4460=7960\frac{35 + 44}{60} = \frac{79}{60}

Step 3 — Simplify: Because 7979 is a prime number and does not divide evenly into 6060, the fraction cannot be simplified further. The final result is 7960\frac{79}{60}.

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Updated 2026-05-02

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