# Teaching Functions and Addends with Fun Machines!

This activity may be the most enjoyable way to introduce and practice functions. It can be adapted to meet the needs of a variety of grade levels.

Preparation: You will need a large box (large enough for a student to sit inside of it). Most appliance stores or big box stores will be happy to donate one. You can have the class decorate it (as a recess or free time activity) or you may choose to decorate it yourself. Turn the box upside down and cut out a “doorway” on one side of the box. Then cut two openings (similar to mailbox slots) on the front of the box and identify them as “in” and “out” slots. Once the “Magic Function Machine” is created, it can be used year after year.

Activity:

1) Have a student sit inside the Magic Function Machine with all needed materials. You can use a variety of items such as counters, dry-erase boards, paper and pencil, craft sticks or any other item you can think of.

2) The Teacher introduces the rule for the function machine. “This Magic Function Machine is so smart; it always adds 5 to any number you tell it. Who wants to try it out?”

3) Choose a volunteer to come to the machine and input a number. They can write in on paper, write it on a whiteboard, count out the correct number of counters, etc. They put this number into the “in” slot in the machine and announce to the class what number they gave the machine (“I am putting in 6 craft sticks.”)

4) Students at their desks figure out what the machine should output while the student in the box does the same.

5) Give the students time to complete the problem. Then, ask the machine to send the output. “I think we are ready. What is the answer Magic Function Machine?”

6) The student inside the box sends the answer through the “out” slot. The student outside the box announces the results to the class. (“I put 6 craft sticks in, and the magic machine gave me 11 craft sticks back.”)

Variations:

1) As students become more proficient, they can create the rule they would like the machine to follow.

2) Practice missing addends (an important algebraic concept). Have the students figure out the rule rather than the output. (“I put in 7 and 10 came out. What rule is the magic machine using?”)

3) The complexity of the problems can change based on the abilities of your students. It is simple to individualize this activity.

4) The problems can vary based on concepts students are practicing (addition, subtraction, multiplication, division, 2-step problems, negative numbers, fractions, etc.)

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