SAMPLE Dental Hygiene Entrance Exam Prep

Dental Hygiene Entrance Exam Preparation Study Guide

3.2 Fractions

3.2.1 Addition and Subtraction of Fractions Begin by converting any mixed numbers (if there are any) into improper fractions. This means convertingany number that represents the sum of a whole numberanda proper fraction into a fraction whose numerator is greater than the denominator. Then you will determine the least common denominator (LCD) for the fractions. The LCD is the smallest common multiple of the denominators. This is the least number that both denominators divide into evenly. Once you have the LCD, then you will rewrite each fraction as an equivalentfractionwith the least commondenominator. Then you will add or subtract the numerators, while keeping the common denominator the same. Lastly, check to make sure that the fraction is the simplest fraction. This means that the only common factor between the numerator and the denominator is 1. Example

Question What is the sum of

Solution

The LCD of 8 and 12 is 24

a. b. c. d.

Therefore, the answer is A.

3.2.2 Multiplication of Fractions First convert any mixed numbers to improper fractions. Then, simplify the factors inthe numerator (the top number in the fraction) with factors in the denominator (the bottom number of the fraction).Lastly, multiply the numerators together and the denominators together. Be sure that the fraction is simplified (the only common factor between the numerator and the denominator is 1).When working with word problems keep in mind that the word “of” usualy signifies multiplication.

Example: Simplify the expression: 1 2 3 × 2 1 7 Since they are mixed numbers, change them to improper fractions: 1 2 3 = 5 3 2 1 7 = 1 7 5

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