7th Grade Math

Add and Subtract Fractions

PARTPART BCBCD E

2

Multi-Part

Lesson

A

Get ConnectED

GLE 0706.2.2

Understand and work with

the properties of and

operations on the system

of rational numbers.

SPI 0706.2.3 Use rational

numbers and roots of perfect

squares/cubes to solve

contextual problems. Also

addresses GLE 0706.1.2,

SPI 0706.2.1.

Main Idea

Add and subtract

mixed numbers.

Add and Subtract Mixed Numbers

BABIES The birth

weights of several

babies in the hospital

nursery are shown.

Birth Weight (pounds)

Jackson 8 _^18

Ajay 7 _^1516

Rebekah 6 _^1316

Mia 5 _^78

1. Write an expression to find how much more Ajay weighs
   than Mia.


2. Rename the fractions using the LCD.


3. Find the difference of the fractional parts of the mixed numbers.


4. Find the difference of the whole numbers.


5. MAKE A CONJECTURE Explain how to find 7 _^15
   16
   
   
   • 5 _^7
     8
     . Then use your
     conjecture to find the difference.
   
   
   
   

To add or subtract mixed numbers, first add or subtract the fractions.

If necessary, rename them using the LCD. Then add or subtract the

whole numbers and simplify if necessary.

Add and Subtract Mixed Numbers

Find 7 _^4

9

+ 10 _^2

9

. Write in simplest form.
Estimate 7 + 10 = 17
7 _^4
9
Add the whole numbers and fractions separately.

+ 10 _^2

9

______

17 _^6

9

or 17 _^2

3

Simplify.

Check for Reasonableness 17 _^23 ≈ 17 ✓

a. 6 _^1

8

+ 2 _^5

8

b. 5 _^1

5

+ 2 _^3

10

c. 1 _^5

9

+ 4 _^1

6

152 Rational Numbers

139_156_C3L2_895130.indd 152 12/31/09 12:37 PM