how-to-multiply-a-fraction-by-a-fraction-and-also-why-it-works-understand-it-conceptually

# Interactive video lesson plan for: How to multiply a fraction by a fraction - and also why it works (understand it conceptually)

#### Activity overview:

Find worksheets to match this lesson at http://www.mathmammoth.com/fractions_2.php

I start out by using visual pie models to show how to multiply a fraction by a fraction means a fractional part OF the other fraction. This way students will understand multiplying fractions conceptually also!

For example, (1/2) x (1/3) means 1/2 of 1/3. Similarly, (1/3) x (1/4) means 1/3 of 1/4.

From these simple fraction multiplications (with unit fractions) we get a shortcut that (1/m) x (1/n) = (1/mn).

Next, we advance to multiplying fractions by fractions. For example, we find what is 2/3 of 1/4 using the concept itself: First, we find 1/3 of 1/4 as being 1/12. Therefore, 2/3 has to be double that much, or 2/12.

After introducing the shortcut for fraction multiplication (multiply the numerators, multiply the denominators), I solve a few simple multiplication problems, missing number problems, and a word problem.

Lastly, I justify the common rule for fraction multiplication (sort of a "proof" for fifth grade level).

This video lesson is meant primarily for 5th grade math but can of course be used for middle school math (and adults) also.

This topic is also explained (along with practice problems) in my book Math Mammoth Fractions 2 at http://www.mathmammoth.com/fractions_2.php - available both as an inexpensive download (\$5.75) and as a printed copy.

If you like the video, please subscribe to my channel to learn more mathematics!

Tagged under: Fifth Grade (Grade Level),math,multiplying fractions,fraction,5th grade math,multiply,fractions,multiply fraction fraction,multiply fractions, grade math, ,mathematics,middle school math,numerators,denominators,word problem

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