1MPES2LCD - Add and Subtract on

Ecole Supérieure de Commerce de Neuchâtel

Pierre Marchal24.09.2015

http://creativecommons.org/licences/by/3.0/Attribute to: Pierre Marchal (Lycée Jean-Piaget)

Objectives of the course

By the end of the course, you should be able to:– Perform prime factorization– Find the LCD– Build up fractions with the same denominator– Add & Subtract any type of fractions:• fractions with a common denominator• fractions with different denominators

Least Common Denominator

• Prime factorization:

• To find the LCD use factors with the exponentshighest

Product of primes

2, 3, 5, 7, 11, 13, …

all

EXAMPLES OF APPLICATION

LCD of 20 and 36

20

1051

LCD :3618931

2 5 3225

2233

2

1

2

4 5 9LCD :

LCD : 180

LCD of 18, 54 and 81

18931

8127931

233

3333

1

5427931

2333

1

LCD : 2 34 2 81LCD : LCD : 162

Practice 1:

• Build up denominators

Practice 1: Solutions

• Build up denominators

Practice 2: Homework

• Find Least Common Denominators:• 16, 34• 18, 25, 27• 12, 13, 14• 15, 18, 24, 25

Practice 3: Homework

• Find LCD and build up fractions:

Add/Subtract - Common Denominators

• Add the and keep the

• Don’t forget to

numeratorsdenominators

reduce

• Common denominator• Add the numerators : 4 + 6 = 10• Keep the denominator: 15

• We get :

• Don’t forget to reduce:

• Common denominator• Subtract the numerators : 27 - 24 = 3• Keep the denominator: 15

• We get :

• Don’t forget to reduce:

Add/Subtract –Different Denominators

• To add and subtract, we the by by themissing

• This means, we have to to find the LCD

build updenominators multiplyin

gfactors

factor

EXAMPLES OF APPLICATION

1. Find the LCD:

421

22

1471

27

2. Find the missing factors:

Missing Factor : 7

Missing Factor : 2

3. Build up denominators:

Exercises

Don’t forget your homework for the next course !

By the end of this course

• You are able to :– Perform prime factorization– Find the LCD– Build up fractions with the same denominator– Add & Subtract any type of fractions:• fractions with a common denominator• fractions with different denominators

Any question ?

THANKS FOR YOUR ATTENTIONEnjoy “Fête des vendanges” but don’t forget to learn your lesson !