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

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 = 12  2 3 5 35 15

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: 3 and 4 are multiplicative inverses because 4 3 3 . 4  1 4 3

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  1 . 7  7 4 7 4 5 20 Dimensional Analysis (212): The process of including units of measurement when you compute.

Let’s Practice! Always put answers in simplest form!! 3 20 1 . 3 4 5 B. 7 . 4 18 21 _ 5 . 3 12 8 D. 1  2 4t . 18r 9r t Did you cross reduce first? 2 27 _ 5 32 7 . 5 = 35 = 7 or 3 1/2 5 2 10 2 2 5 1 2 8 t 2

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

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