5-6 Least Common Multiple
page 226-230
A multiple of a number is a product
of that number and a whole number.
Multiples of 4: 0, 4, 8, 12, 16, 20, 24, 28, ….
Multiples of 6: 0, 6, 12, 18, 24, 30, 36, 42, ...
The least of the nonzero common multiples is called
the least common multiple (LCM). So, the LCM of
4 and 6 is 12.
5-6 Least Common Multiple
page 226-230
A multiple of a number is a product
of that number and a whole number.
Multiples of 4: 0, 4, 8, 12, 16, 20, 24, 28, ….
Multiples of 6: 0, 6, 12, 18, 24, 30, 36, 42, ...
The least of the nonzero common multiples is called
the least common multiple (LCM). So, the LCM of
4 and 6 is 12.
Example 1 Ladder Method Find the LCM of 108 and 240
108
2
240
54
2
120
27
3
1
60
9
20
9
20
Multiple 2 2 3 1 9 20
The LCM of 108 and 240 is 2160
Example 2
Finding LCM of Monomials
18xy2
10y
233xyy
25y
2y33xy5
shared
left over
LCM = 90xy2
Try It
12x2y2
6y3
12x2y3
Find the Least Common Denominator of
the algebraic fractions.
9
36a2b
16
27ab2
108a2b2
Comparing Fractions
Cross Multiply
1
6
7
15
Or:
Find LCD and make equivalent
fractions...place on number line to
compare.
5
30
14
30
Unlike Fractions have different denominators!
We write all +/- fraction problems vertically!
1
4
+
2
3
Find LCD
Make equivalent fractions
+/Simplify