Adding Fractions
2/6 +3/6
5/6
What is the common denominator of 6/8 and 2/3?
8: 8,16,24
3: 3,6,9,12,15,18,24
CD is 24
7/8 - 3/8
4/8 = 1/2
Tiffany bought 2/5 g of cherries. Linda bought 1/10 g of cherries less than Tiffany. How many grams of cherries did they buy together?
7/10
Show on whiteboard
1/4 + 3/5
4: 4,8,12,16,20
5: 5,10,15,20
1/4= 5/20 3/5= 12/20
5/20+12/20=17/20
What is the common denominator for 4/3 and 1/2?
3: 3,6
2: 2,4,6
CD is 6
2/3- 3/5
3: 3,6,9,12,15
5: 5,10,15
2/3= 10/15 3/5= 9/15
10/15 - 9/15 = 1/15
Matt sold 1/4 gallon of lemonade one day. On day two and three he sold 5/8 gallon. How much did Matt sell all together?
1/4= 2/8
2/8 + 5/8+ 5/8 = 12/8= 1 1/2
3/5 + 1/2 + 1/5
4/5 + 1/2
1/2= 5/10 4/5= 8/10
5/10 + 8/10= 13/10= 1 3/10
What is the common denominator between 3/15, 2/3, and 1/5
5: 5,10,15
3: 3,6,9,12,15
15: 15
CD is 15
4/5- 1/5- 1/3
3/5 - 1/3
5: 5,10,15 3: 3,6,9,12,15
9/15 - 5/15 = 4/15
Ribbon A is 1/3 meter long. It is 2/5 m shorter than Ribbon B. What is the length of Ribbon B?
11/15
Do on whiteboard
1 3/4 + 2/3
1 3/4= 7/4= 21/12
2/3= 8/12
21/12 + 8/12= 29/12= 2 5/12
When trying to find the common denominator, without drawing fraction models, hw do you find it?
Think of your multiplication facts or do the skip counting to find same multiples
1 1/4- 2/6
4: 4,8,12 6: 6,12
1 1/4= 5/4= 15/12 2/6= 4/12
15/12 - 4/12 = 11/12
1 1/15 m long
1 1/3 + 3/5
1 1/3= 4/3= 20/15
3/5= 9/15
20/15 + 9/15= 29/15= 1 14/15
When do you need to find a common denominator?
When the adding or subtracting problems have different denominators.
4 2/5 - 2 2/3
5: 5,10,15 3: 3,6,9,12,15
4 2/5= 22/5= 66/15
2 2/3= 8/3= 40/15
66/15 - 40/15 = 26/15= 1 11/15
What are the steps to solving a word problem?
RDW, Draw a picture, Show math, Make a sentence, and don't forget units.