Adding and Subtracting Fractions w/ Unlike Denominators

Adding Fractions w/ unlike denominators

100

2/3 + 1/4

11/12

200

3/4 + 2/3

17/12

300

4/5 + 3/4

 

31/ 20

400

6/7 + 5/6

71/ 42

500

1/2 + 1/3 

5/6

Subtracting fractions w/ unlike denominators

100

1/3 - 1/4

                                             

1/12

200

2/3 - 1/5

                                              

7/15

300

1/2 - 1/5 

                                             

3/10

 

400

4/5 - 2/3

2/15

500

5/7 - 1/3

 

8/21

 

Estimating

100

Round each fraction to 0, 1/2, or 1 to estimate the total

2/5 + 7/10

0 + 1 = 1

200

Round each fraction to 0, 1/2 , or 1 then estimate the answer

7/8 - 2/4

1 - 1/2 = 1/2

300

Round each fraction to 0, 1/2, or 1, then estimate the answer

7/8 + 1/12

1 + 0 = 1

400

Round each fraction to 0, 1/2, or 1, then estimate the answer

4/9 + 1/6

1/2 + 0 = 1/2

500

Round each fraction to 0, 1/2, or 1, then estimate the answer

5/12 - 1/6

1/2 - 0 = 1/2

Adding & Subtracting Fractions in the same problem

100

1/2 + 1/4 - 1/8

1/2 + 1/4 = 2/4 + 1/4 = 3/4

3/4 - 1/8 = 6/8 - 1/8 = 5/8

Answer is 5/8

200

5/6 - (1/4 + 1/3) 

1/4 + 1/3 = 3/12 + 4/12 = 7/12

5/6 - 7/12 = 10/12 - 7/12 = 3/12

Answer is 3/12

300

If I had 1/3 of a cake and you had 1/2 of the cake. How much did we have all together? How much was left for everyone else? 

1/3 + 1/2 = 2/6 + 3/6 = 5/6

We had 5/6 of the cake.

6/6 - 5/6 = 1/6          1/6 is left for everyone else.

400

(7/20 + 1/5) - 3/10

7/20 + 1/5 = 7/20 + 4/20 = 11/20

11/20 - 3/10 = 11/20 - 6/20 = 5/20 

Answer is 5/20 or 1/4 (they are equivalent) 

500

Sam only gets a small amount of screen time on weekends. He lost some of it for poor choices so now only has 7/8 of his original time left for the weekend.
He used 1/3 on Saturday morning and 1/4 on Saturday afternoon. How much does he have left for Sunday? 

7/8 - (1/6 + 1/4) 

1/6 + 1/4 = 2/12 + 3/12 = 5/12 used

7/8 - 5/12 = 21/24- 10/24= 11/24 

Answer: He has 11/24 of his time left.

Word Problems

100

Betty mixed 1/6 pound of peanuts with 1/3 pound of raisins. How much mix did Betty have in all?

1/6 + 1/3 = 1/6 + 2/6 = 3/6 or 1/2 pound

200

Jill did aerobics for 3/5 hour then lifted weights for 1/3 hour. How long did she exercise for in total?

3/5 + 1/3 = 9/15 + 5/15 =14/15 hour

300

Justin used 3/4 pound of broccoli to make a stir-fry and 9/10 pound of broccoli to make cheddar broccoli soup. How much broccoli did he use all together? 

3/4 + 9/10 = 15/20 + 18/20 = 33/20 pounds

400

Matt jogged 1/2 of a mile. Thomas jogged 5/8 of a mile. How much farther did Thomas jog than Matt? 

5/8 - 1/2 = 5/8 - 4/8 = 1/8

Answer - he jogged 1/8 of a mile farther

500

At 2 P.M. Todd noticed he had 7/8 power left on his smartphone. At 5 P.M. He had 2/3 power left. How much power did Todd use between 2 P.M. and 5 P.M.? 

7/8 - 2/3 = 21/24- 16/24 = 5/24 power