5th Grade Math Lessons: Introduction to Fractions

5th Grade Fraction Lessons

Fractions with Unlike Denominators

Up until 5th grade, students have only added and subtracted fractions with the same denominator. As a result, a problem like 5/12 + 2/3 might look intimidating to some kids. Tell your child that the first thing to do with problems like this is to make the denominators the same.

First, identify the least common denominator for the fractions. One way to do this is by multiplying the top and bottom of each fraction by the denominator of the other fraction. For the problem 1/2 + 1/3, you could multiply one and two by three, like this: (1 x 3)/(2 x 3). Then, you'd multiply one and three by two, like this: (1 x 2)/(3 x 2). The resulting fractions are 3/6 and 2/6. Last, you can add like normal (3/6 + 2/6 = 5/6).

However, that isn't always necessary. Using the example above (5/12 + 2/3), you can simply multiply the second fraction by four to get the same denominator. Be sure to multiply both the numerator and the denominator by four so 2/3 becomes 8/12. Then, add like so: 5/12 + 8/12 = 13/12.

Name that Denominator!

After your child understands the basics, he or she can practice in a fun way by playing this game. Write a variety of fraction problems with unlike denominators on index cards, and place them upside down on a table. To play, flip over one card at a time. The player who correctly identifies the least common denominator first wins that card. The player with the most cards at the end of the game wins.

Whole Number Multiplication

Your 5th grader will also begin learning to multiply a fraction by a whole number. To do this, first turn the whole number into a fraction by putting it over one. For example, if you wanted to multiply 3/5 x 7, you would turn seven into 7/1. Then, multiply the numerators together and the denominators together. The answer should look like this: 3/5 x 7/1 = (3 x 7)/(5 x 1) = 21/5.

Triple a Recipe

To practice, give your child a recipe and ask him or her to triple it. As a result, your child will have to multiply all of the measurements by three. Let's say a cookie recipe calls for 3/4 of a cup of sugar. Our initial equation is 3/4 x 3. Turn the integer (three) into a fraction (3/1). Then, multiply across: 3/4 x 3/1 = 9/4.

Now, your child will have to change the improper fraction (9/4) into a mixed number. Divide the numerator by the denominator, like this: 9 ÷ 4 = 2 R1. Two is the integer for our mixed number. Then, put the remainder (one) over the denominator (four) to finish. As a result, in the new recipe, you will need 2 1/4 cups of sugar.