The Procedure
True or False: You can add and subtract fractions while the denominator is different.
False: You have to have a common denominator.
What is the LCM of 2 and 8?
8
2/5 = ?/15
6/15
3/6 + 1/6 = ?
4/6
1/4 + 1/3=?
7/12
What is the first step in adding or subtracting two unlike fractions?
Finding the LCM or Least Common Multiple.
What is the LCM of 4 and 5?
20
1/3 = /27
9/27
3/14 + 5/14= ?
8/14
3/7 + 2/5 =?
29/35
How do you make an equivalent fraction?
You have to divide or multiply the numerator and denominator by the same numbers.
What is the LCM of 3 and 5?
15
3/5 = ?/45
27/45
15/20 - 8/20=?
7/20
2/5 - 1/10=?
3/10
True or False: If one of the fractions already has the common denominator then you don't have to transform it.
True. You just have to transform the other into an equivalent fraction with a matching denominator.
What is the LCM of 12 and 8?
24
4/10 = ?/30
12/30
6/8- 2/8 =?
4/8 or 1/2
6/10 - 1/2=?
1/10
What do you do when you have two like fractions at the end?
Add or subtract across the numerator and keep the denominator.
What is the LCM of 9 and 12?
36
11/12 =?/48
44/48
32/45 - 20/45=?
12/45
8/10-2/3 =?
4/30 or 2/15