Computing with Rational Numbers

Computing with Rational Numbers

Adding Rational Numbers

• Same Signs: add the two numbers together and keep the sign

• Examples: 3 + 4 = 7 and -9 + -1 = -10

• Different Signs: SUBTRACT the smaller number from the bigger and keep the sign of the number with the bigger absolute value

• Examples: -7 + 10 = 3 and 5 + -6 = -1

Multiple Choice

-8 + 10 =

• 18

• -18

• 2

• -2

Multiple Choice

-4 + -10 =

• 14

• -14

• 6

• -6

Multiple Choice

-6.4 + 9.2

• 2.8

• -2.8

• 15.6

• -15.6

Subtracting Rational Numbers

• KEEP, CHANGE, FLIP

• Keep the first number, change subtraction to addition, flip the sign of the second number

• Example: 5 - 10 becomes 5 + (-10)

• Solve the addition problem.

Multiple Choice

(-6) - (-4) =

• 2

• -2

• 10

• -10

Multiple Choice

7 - 12 =

• 19

• -19

• 5

• -5

Multiple Choice

 $\frac{1}{2}-\frac{3}{4}=$  

•  $\frac{1}{4}$  

•  $-\frac{1}{4}$  

• 1

• -1

Multiplying Rational Numbers

• Same Signs: POSITIVE ANSWER

• Example: -9 x (-5) = 45

• Different Signs: NEGATIVE ANSWER

• Example: -9 x 5 = -45

Multiple Choice

 $-3\times5=$  

• 15

• -15

Multiple Choice

 $-4\times-8=$  

• 32

• -32

Multiple Choice

 $6.34\ \times\left(-3.5\right)=$  

• 22.19

• -22.19

Dividing Rational Numbers

• Same Signs: POSITIVE ANSWER

• Example:

   $-9\div\left(-3\right)=3$  

• Different Signs: NEGATIVE ANSWER

• Example:  $15\div\left(-3\right)=-5$  

Multiple Choice

 $-16\div4=$  

• 4

• -4

Multiple Choice

 $-35\div\left(-7\right)=$  

• 5

• -5

Multiple Choice

 $-52.2\div3.6=$  

• 14.5

• -14.5