In order to add two fractions, we must first make sure we can find the LCD of the two fractions first.[br][br]The LCD is the Least Common Denominator of the 2 fractions. We can find it by finding the least common multiple of the denominators.[br][br]So we keep adding the denominators onto themselves until we find the least common one.

Use the model below to visualize adding fractions using the least common denominator.

Move the sliders to manipulate the numerators and denominators of both fractions.[br][br]We can go up to 10/10 on both sides. [br][br]Match the given numbers, then slide one diagram onto the other to get the LCD.