+ fractions: addition & subtraction algebra seminar 2012-2013
TRANSCRIPT
+
Fractions: Addition & Subtraction Algebra Seminar 2012-2013
Two Fractions can be combined easily when they have a common denominator.
8
7
8
5+
12
43
12
55 +
5
10+
410
13
8+ 4
28
+
Def. Common Denominator- A number that all of the denominators divide into evenly.
+Common Denominator (similar to LCM)
A number all original denominators divide into evenly
12 is a common denominator because 3 and 4 both divide 12 evenly.
3
2
4
3
Least Common Denominator (same as LCM)
To find the least common denominator
* Write the times table list for each denominator
* The smallest number that is in all rows is the least common denominator
+Least Common Denominator
To find the least common denominator• Write the times table list for each denominator• The smallest number that is in all rows is the
least common denominator
+The least common denominator is: 24!!!
so5
6+
34
+78
=2024
+1524
+2124
=5624
=72
=312
+Practice - Find the common denominator for these fractions.
2/3 + 3/5
¾ + 7/12
2/5 + 3/8 + 7/10
What if the denominators do NOT match? If the denominators do not match, you must
find the LCM to change them.
12
51
12
17
12
8
12
93
2
4
3
=
=+
=+5
8+
13
=
1524
+824
=2324
+
Subtracting Fractions
+Subtraction – the process is the same but you will subtract the numerators instead of adding them.
Squirt reminds you to:
1) Get a Common Denominator
2) Subtract
7
8−
34
=
78
−68
=18
+Extra Practice
7
8−
14
=
5
6−
35
= 14
15−
39
=
7
10−
25
=
+Subtraction
What is different about this problem? We have a mixed number!
Lets change them to improper
fractions!
42
5−2
35
=
22
5−
135
=9
5=1
45
Subtraction Practice
73
4−2
56
=
16
10−
46
=
32
4−1
35
=