Find the LCD
1/3 - 1/5
What is the LCD?
3: 3, 6, 9, 12, 15
5: 5, 10, 15
The LCD is 15
1/2 + 1/4
1/2 + 2/4
3/4
I want to bake a cake. I add 2/3 flour and 1/4 sugar. How much did I mix together?
The denominators are denomi-neighbors so I can multiply them by each other to get 12.
4/12 + 3/12 = 7/12
3/15
We can divide it by 3 to simplify it to 1/5
6/8 - 3/8
3/8
1/2 + 1/4
What is the LCD?
2: 2, 4
4: 4
The LCD is 4
1/6 + 2/3
The denominators are related so the common denominator is 6.
5/6
Jenny is building a tree house. She has 1/2 a yard of wood and cuts off 1/3. How much wood does she have left?
The denominators are denomi-neighbors so I can multiply them by each other to get a common denominator of 6.
3/6 + 2/6 = 1/6
4/6
We can divide it by 2 to simplify it to 2/3
7/9 - 5/9
2/9
1/5 - 1/6
What is the LCD?
5: 5, 10, 15, 20, 25, 30
6: 6, 12, 18, 24, 30
30 the is LCD
3/4 + 1/5
4: 4, 8, 12, 16, 20
5: 5, 10, 15, 20
15/20 + 4/20 = 9/20
I want to create a bow to tie my Christmas presents. I tied 4/5 blue ribbon and 2/3 red ribbon together. How much ribbon did I tie altogether?
5: 5, 10, 15
3: 3, 6, 9, 12, 15
The LCD is 15.
12/15 + 10/15 = 22/15
1 and 7/15 ribbon
12/15
We can divide it by 3 to simplify it to 4/5
1 2/7 - 2/7
1
3/9 + 4/6
What is the LCD?
9: 9, 18
6: 6, 12, 18
The LCD is 18
3/5 + 5/6
The denominators are number neighbors so we can multiply them times each other.
18/30 + 25/30
43/30
1 and 13/30
Mr.Frankum needed stuff to fill his aquarium. He filled 1/9 with sand and 1/6 with mulch. How much more mulch does he have than sand?
9: 9, 18
6: 6, 12, 18
The LCD is 18
3/18 - 2/18 = 1/18
6/12
We can divide it by 3 to get 2/4 and then divide it by 2 to get 1/2
Or you can see that 6 is half of 12 so it simplifies to 1/2
1 1/5 - 3/5
6/5 - 3/5
2/5
3/12 + 1/3
What is the LCD?
12: 12
3: 3, 6, 9, 12
The LCD is 12
3/4 + 1/3
The denominators are denomi-neighbors so I can multiply them by each other to get an LCD of 12.
9/12 + 4/12 = 13/12
1 and 1/12
Mrs.Armstrong wants to put christmas lights around her tree. She put 5/8 yards of white lights and 3/4 yards of red lights. How many yards of red lights does she have than white lights?
The denominators are related so the LCD is 8. I only need to change one fraction.
6/8 + 5/8 = 1/8
15/35
They both end in a 5 so it can be simplified by 5.
It simplifies to 3/7
2 1/6 - 1 5/6
13/6 - 11/6
2/6
It can be simplified to be 1/3