7th Grade Math

Use fraction strips to find ^78 - ^34.

Model each fraction.

1

8

1

8

1

8

1

8

1

8

1

8

1

8

1

4

1

4

1

4

1

4

1

4

1

4

7

8

3

4

To subtract, line up the 1

8

1

8

1

8

1

8

1

8

1

8

1

8

-^1
4

1

4

1

4

1

4

1

4

1

4

7

8

3

4

ends of the shaded parts

of each strip.

Test different fraction^1

8

1

8

1

8

1

8

1

8

1

8

1

8

1

8

-^1
4

1

4

1

4

1

4

1

4

1

4

7

8

1

8

3

4

The marks

line up.

strips below the model,

checking to see if the

marks line up. Then

shade the sections

between the beginning

of the strip and the

point where they line up.

So, 78 - ^34 = _^18.

and Apply

Use fraction strips to add or subtract.

1. 101 + ^25 2. ^16 + ^12 3. 21 + 43


2. 83 - ^14 5. ^89 - ^13 6. 32 - 41

the Results

Use the models from Activities 1 and 2 to complete the following.

7. ^12 + ^15 = 10 + 10 8. 87 - ^34 = ^8 - ^8


8. MAKE A CONJECTURE What is the relationship between the number of
   separations on the answer fraction strip and the denominators of the
   fractions added or subtracted?


9. E WRITE MATH Two thirds of the baseball team at Park Street Middle
   School lives within walking distance of the practice field. Another _^16 of the
   team lives close enough to ride their bike. What fraction of the team lives
   close enough to the practice field to walk or ride their bike there? Explain
   your reasoning.

Lesson 2B Add and Subtract Fractions 145

139_156_C3L2_895130.indd 145 12/31/09 12:37 PM