using lowest common denominator to add and subtract fractions

Mr. Coon’s Math Class

The answer to a multiplication problem.

6 X 6 = 36

7 X 8 = 56

8 X 9 = 72

The product of a whole number multiplied times any other whole number.

Some multiples of 6 6, 12, 18, 24, 30, 36, 42

5, 10, 15, 20, 25, 30, 35

7, 14, 21, 28, 35, 42, 49

4, 8, 12, 16, 20, 24, 28

9, 18, 27, 36, 45, 54, 63

A number that is a multiple of two or more numbers.

Some multiples of 3 & 6

6, 12, 18, 24, 30, 36, 42

8, 16, 24, 32, 40, 48, 56

12, 24, 36, 48, 56, 60

21, 42, 63

10, 20, 30, 40, 50, 60

The smallest common multiple of a set of two or more numbers.

6 = 6, 12, 18, 24, 30, 36

5 = 5, 10, 15, 20, 25, 30

8 = 8, 16, 24, 32, 40, 48 3 = 3, 6, 9, 12, 15, 21, 24

8 = 8, 16, 24, 32, 40, 48 4 = 4, 8, 12, 16, 20, 24

8 = 8, 16, 24, 32, 40, 48 6 = 6, 12, 18, 24, 30, 36

10 = 10, 20, 30, 40, 50, 4 = 4, 8, 12, 16, 20, 24

9 = 9, 18, 27, 36, 45, 54 3 = 3, 6, 9, 12, 15, 21,

Find the multiples of each denominator.

1= 5, 10, 15, 20, 25, 30

1= 10, 20, 30, 40, 50+

5

10

Compare the lists of multiples. Circle the common multiples between the two lists.

15 = 5, 10, 15, 20, 25, 301

10 = 10, 20, 30, 40, 50+

Use the lowest common multiple as the denominator.

15 = 5, 10, 15 ,20 ,25 ,301

10 = 10, 20, 30, 40, 50+

This number is also called the least common denominator.

15 = 5, 10, 15 ,20 ,25 ,301

10 = 10, 20, 30, 40, 50+

12 = 2, 4, 6, 8, 10, 1218 = 8, 16, 24, 32, 40+

110 = 10, 20, 30, 40, 18 = 8, 16, 24, 32, 40+

110 = 10, 20, 30, 40, 14 = 4, 8, 12, 16, 20, +

12 = 2, 4, 6, 8, 10, 14 = 4, 8, 12, 16, 20, +

12 = 2, 4, 6, 8, 10, 12 112 = 12, 24, 36, 48 +

13 = 3, 6, 9, 12, 15 14 = 4, 8, 12, 16, 20, +

13 = 3, 6, 9, 12, 15 15 = 5, 10, 15, 20, 25, +

13 = 3, 6, 9, 12, 15 19 = 9, 18, 27, 36, 45, +

1319+

Check to see if the smaller denominator divides evenly into the larger denominator.If it does, use the larger denominator for your LCD or LCM.

3 will divide evenly into 9, so 9 is your LCD or LCM.

1214+

Using the shortcut, what is the LCD or LCM?

2 will divide evenly into 4, so 4 is your LCD or LCM.

12110+

Using the shortcut, what is the LCD or LCM?

2 will divide evenly into 10, so 10 is your LCD or LCM.

12112+

Using the shortcut, what is the LCD or LCM?

2 will divide evenly into 12, so 12 is your LCD or LCM.

1418+

Using the shortcut, what is the LCD or LCM?

4 will divide evenly into 8, so 8 is your LCD or LCM.

1316+

Using the shortcut, what is the LCD or LCM?

3 will divide evenly into 6, so 6 is your LCD or LCM.

13112+

Using the shortcut, what is the LCD or LCM?

3 will divide evenly into 12, so 12 is your LCD or LCM.

13115+

Using the shortcut, what is the LCD or LCM?

3 will divide evenly into 15, so 15 is your LCD or LCM.

1318+

Using the shortcut, what is the LCD or LCM?

3 will not divide evenly into 8, so find the least common multiple.