Multiplication of Fractions As Repeated Addition

Multiplication of fractional numbers can be represented as repeated addition.

Background information: A numeral like 1/5 is a fraction. It can be thought of as one out of a group of five. 1/5 of the class has red hair, or one person out of every five has red hair.

Represented with Cuisenaire rods:

If Yellow = one,

then 3 x 1/5 =

1/5 + 1/5 + 1/5 or 3/5

Activity: Illustrate multiplication of a whole number and fractional number by joining the number of fractional parts.

Solve problems like the following:

If you have three opened packs of chewing gum and each has one stick out of five left, then you have 1/5 + 1/5 + 1/5 or 3/5.

Therefore 3 x 1/5 = 1/5 + 1/5 + 1/5 or 3/5

Illustrate solutions for problems like the following.

3 x 1/4	2 x 1/5
4 x 1/6	3 x 1/4
7 x 1/3	5 x 2/3
3 x 4/5

 

Dr. Robert Sweetland's Notes ©