1 2 + 1 9 = ? The Least Common Multiple (LCM) of 2 and 9 is 18. Multiply the numerator and denominator of each fraction by whatever value will result in the denominator of each fraction being equal to the LCM: 1 2 + 1 9 = 1 × 9 2 × 9 + 1 × 2 9 × 2 = 9 18 + 2 18 Now that the fractions have like denominators, add the numerators: 9 18 + 2 18 = 9 + 2 18 = 11 18 The result is: 1 2 + 1 9 = 11 18