1. Chapter 5 Lessons 3 & 4 Multiplying (5-3) & Dividing (5-4) Rational Numbers Pgs. 210-219
What you will learn:
Multiply fractions
Divide fractions using multiplicative inverses
Use dimensional analysis to solve problems

2. Key Concepts:
Multiplying Fractions (210):
Words: To multiply fractions, multiply the numerators and
multiply the denominators.
Symbols: a . c = ac , where b,d  0
b d bd
Example: = 12  2 

3. Key Concepts:
Inverse Property of Multiplication (215):
Words: The product of a number and its multiplicative
inverse is 1
Symbols: For every number a , where a, b  0, there is b
exactly one number b such that a . b  1
a b a
Example: and 4 are multiplicative inverses because
 1
4 3

4. Key Concept:
Dividing Fractions (216):
Words: To divide by a fraction, multiply by its multiplicative
inverse (reciprocal).
Symbols: a  c  a . d , where b,c,d  0
b d b c
Example: 1  5   7
Dimensional Analysis (212): The process of including units
of measurement when you
compute.

5. Let’s Practice! Always put answers in simplest form!!3 20
1 . 3
4 5 B _
D  2
4t . 18r
9r t
Did you cross reduce first? 2 27
_ 5 32
= 35 = 7 or 3 1/2 2 5 1 2 8 t 2

6. 2 7  5 Keep on Practicin’ !! Remember: Answers in simplest form!
What is the multiplicative inverse (reciprocal)?
_ 3 8 2
1  6
7  5
E. X  AX
_ 8 3 5 11 1 5 7 12 1 3
22  5 = = 22 or 1 7/15 2 2x 5a

7. Homework:
Posted by the door!
Let’s look at dimensional analysis problems
on the interactive chalkboard!!