RadfordMathematics.com

Adding & Subtracting with Fractions

(Least Common Multiple - Least Common Denominator - LCD)

We learn a second method for adding and subtracting with fractions. \[\frac{a}{b}+\frac{c}{d} \quad \text{and} \quad \frac{a}{b}-\frac{c}{d}\] The trick is two write each of the two fractions over the same denominator. The denominator over which we write the fractions is equal to the least common multiple, LCM, of the denominators; this LCM is known as the least common denominator.

Tutorial: Adding & Subtracting Fractions

We learn how to add and subtract with fractions, using the least common multiple of the fractions' denominators.

Exercise 1

Using the method we've just seen, calculate each of the following additions with fractions:

  1. \(\frac{3}{4}+\frac{1}{6}\)
  1. \(\frac{2}{3} - \frac{2}{5}\)
  1. \(\frac{1}{6}+\frac{3}{5}\)
  1. \(\frac{3}{11} - \frac{5}{33}\)
  1. \(\frac{3}{7}+\frac{1}{2}\)
  1. \(\frac{7}{9} - \frac{2}{6}\)
  1. \(\frac{2}{5}+\frac{3}{7}\)
  1. \(\frac{3}{4} - \frac{2}{5}\)
  1. \(\frac{1}{8}+\frac{2}{3}\)
  1. \(\frac{3}{4} - \frac{5}{8}\)
  1. \(\frac{3}{8}+\frac{5}{12}\)
  1. \(\frac{4}{5} - \frac{2}{3}\)
  1. \(\frac{5}{9}+\frac{1}{3}\)
  1. \(\frac{3}{4} - \frac{5}{8}\)
  1. \(\frac{7}{12}+\frac{3}{8}\)
  1. \(\frac{7}{8} - \frac{5}{6}\)

Note: this exercise can be downloaded as a worksheet to practice with: Worksheet 1

Scan this QR-Code with your phone/tablet and view this page on your preferred device.

Subscribe to Our Channel

Subscribe Now and view all of our playlists & tutorials.