Finding a Common Denominator : 3, 6, 9, 12, 15, 18… 1 3 3 : 2 5, 10, 15, 20, 25, 30…  Now you have found the LCM. 5 5 First you need to find the LCM. Now you need to list the multiples for each number.

Finding a Common Denominator Time to add the fractions. 15 1 X 5 = 5 3 X 5 = 2 X 3 = 6 15  Your LCM is now your CD for the addition Problem. 5 X 3 = Use the factor that brought you to your multiple on the numerator. Multiple across to find your new equivalent fraction. Now apply the same rule for the bottom fraction.

Finding a Common Denominator It doesn’t get any easier than that. The denominator will be the same. Use addition on the numerators. 1 X 5 = 5 3 X 5 = 15 2 X 3 = 6  5 X 3 = 15 11 15