# Adding and Subtracting Fractions - PowerPoint PPT Presentation

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### Title: Adding and Subtracting Fractions Author: LHCA Last modified by: Pamela Jenkins-Sanford Created Date: 6/27/2008 12:07:24 AM Document presentation format – PowerPoint PPT presentation

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1
• By Graeme Henchel

http//hench-maths.wikispaces.com
2
3
Problem You cant add fractions with different
denominators without getting them ready first.
denominators
Solution Turn fractions into equivalent
fractions with a common denominator that is find
the Lowest Common Multiple (LCM) of the two
denominators
4
Finding the Lowest Common Denominator
• The lowest common multiple of two numbers is the
lowest number in BOTH lists of multiples

Multiples of 2 are 2, 4, 6, 8, 10 Multiples of
3 are 3, 6, 9, 12, What is the lowest
common multiple?
5
Finding the Lowest Common Denominator
• The lowest common multiple of two numbers is the
lowest number they will BOTH divide into

2 divides into 2, 4, 6, 8.. 3 divides into 3, 6,
9. What is the lowest number 2 and 3 both
divide into?
6
You cant add fractions with different
denominators

The Lowest Common Multiple of 2 and 3 is 6 so
turn all fractions into sixths
Special form of 1
7
Lowest common denominator is 10 so make all
fractions tenths
8
Turn both fractions into twelfths