Constant Function Calculator Activities    blackdouglas.com.au

Children are constantly fascinated by the Constant Function of a calculator which constantly repeats the last operation it was asked to do if the [=] button is constantly pressed.

• We can make use of this interest to encourage a little thinking.
• The way the constant function is accessed could be different to the examples given here.
• If unsure, check the instructions - or ask the children!

Procedure

Press [+] then a number. eg:

Now press [=] again. The calculator will repeat the previous operation ... [+] [4] ... to give an answer of 8. With each on-going press of [=] another [+] [4] will occur until the operation is changed, or cleared.

• Can you predict the next number?
  • Guess then check.
• How many times will you press [=] to reach 40?
  • Guess then check.

Discuss and record the patterns noticed.

Variations

1. Subtraction using the constant function. eg:

[1] [0] [0] [0] [-] [1] [0] [=]

990

[=]

980

[=]

970 ...

2. Doubling, eg:

[2] [x] [3] [=]

6

[=]

12 ...

3. Halving, eg:

[1] [0] [0] [0] [÷] [2] [=]

500 ...

4. Close Your Eyes Counting

• An example is to start with zero on the screen and teach the calculator to count forward by 7 (say) by pressing [+] [7].
• Now, close your eyes and press [=] until you think the screen will show 84 (say).
• Open your eyes. Were you correct?
• Try counting backwards.

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