# Factor That

```Single Function Machine
Numbers are entered into a function machine
1, 2, 3, 4 ….
2, 4, 6, 8 …
These numbers
come out
What is happening to the numbers?
What is happening?
Numbers are entered into a function machine
1, 2, 3, 4 …
2, 3, 4, 5 …
These numbers
come out
What is happening?
Numbers are entered into a function machine
10, 20, 30, 40 …
5, 10, 15, 20 …
These numbers
come out
Using the TI-15 Explorer™
• Locate the op1 key 
• This key operates like a function machine.
• To simulate a function machine that doubles
the numbers press  x2 .
• Enter 5 into your calculator press  .
The display should show 10.
Using the TI-15 Explorer™ 2
• Use the  key to create your own function
machine questions.
• Write your questions on the single function
machine worksheet.
• Remember to keep a copy of your
• Give a copy of your question sheet to a
partner to solve.
Reverse Function Machine
What happens if the function machine is set in reverse?
1, 2, 3, 4 ….
2, 4, 6, 8 …
These numbers are
fed into the machine
What is happening to the numbers?
Reverse Function Machine 2
What happens if the function machine is set in reverse?
1, 2, 3, 4 ….
2, 3, 4, 5 …
These numbers are
fed into the machine
What is happening to the numbers?
Reverse Function Machine 3
What happens if the function machine is set in reverse?
10, 15, 20, 25 ….
20, 30, 40, 50 …
These numbers are
fed into the machine
What is happening to the numbers?
• What do you notice happens to the
operation when a function machine is set
in reverse?
• Explore your ideas using the  key on your
TI-15 Explorer™ calculator
Forward and Reverse
• + and – are inverse operations
If the function machine adds 2, then when it
is put in reverse it would subtract 2
• X and ÷ inverse operations
If the function machine multiplies by 10,
then when it is put in reverse it will
divide by 10
What Happens When Two Function
Machines Are Joined?
1, 2, 3, 4 ….
+2
+3
Test it out using the  and  keys on your
TI-15 Explorer™ calculator
1, 2, 3, 4 ….
+5
–2
Multiplication
1, 2, 3, 4 ….
x2
x5
Could I replace two function machines with one machine?
What single machine could replace the two machines?
Multiplication and Division
1, 2, 3, 4 ….
x 10
÷
2
What happens when you join two division function
machines?
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```

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