Rational Number Operations

Rational Number Operations

TEKS 7.3B

Adding Positive and Negative Numbers

When adding a positive and negative number, ​always SUBTRACT the smaller absolute value from the larger absolute value and give the difference the same sign as the number with the LARGER absolute value.

​

​3 + (-6) = ??

​

​Subtract the absolute values :

|6| - |3| = 3

​

​Give the difference the sign of the larger absolute value (-6):

3 +(-6) = -3

Multiple Choice

-2 + 4 = ?

• 6

• -6

• -2

• 2

Multiple Choice

-8 + 5

• 13

• -3

• -13

• 3

​Subtracting Positive and Negative Numbers

​When subtracting positives and negatives, use the "adding the opposite rule." It is very similar to "KCF."

​Example: (-4) - 7 = ?

​Step 1: Rewrite the sentence above into an addition sentence

​(-4) - 7 = ? becomes (-4) + 7 = ?

​Step 2: Change sign of the second number to its opposite

​(-4) + 7 = ? becomes (-4) + (-7) = ?

Step 3: Follow the Adding Rational Number rules ​

​(-4) + (-7) = - 11

Multiple Choice

-6 - 7

• 1

• 13

• -1

• -13

Multiple Choice

$$-\frac{2}{5}-\left(-\frac{4}{5}\right)=?$$  

• $$-\frac{6}{5}$$  

• $$\frac{2}{5}$$  

• $$1\frac{1}{5}$$  

• $$-\frac{2}{5}$$  

​Multiplying and Dividing Rational Numbers

​When multiplying or dividing numbers with the same sign, the answer will ALWAYS be positive:

​- 4 x -.5 = 2 | 5 ÷ 2 = 2.5

​

​​When multiplying or dividing numbers with different signs, the answer will ALWAYS be negative:

​​- 4 x .5 = -2 | 5 ÷ -2 = -2.5

Multiple Choice

$$-2\ \div\ -11\ =\ ?$$  

• .18...

• 5.5

• -.18...

• -5.5

Multiple Choice

$$-5.5\ \times\ 10.5=?$$  

• -57.75

• 577.5

• 57.75

• -5775