What
to do: Part 2
 Take turns subtracting a number between 1 and 9 inclusive
from the number displayed.
 The person who avoids making the calculator display zero is
the winner.


Tips
and Tricks for the Teacher

Play a game with the whole class discussing & demonstrating number
strategies.
 Model a few games in front of the class with: one calculator for
you & one for each pair of students  computer calculator on IWB
or data projector  draw the calculator display on the whiteboard.
 'You are not to change the numbers in any other column. Only the
column stated'.
 'Don't forget to press the subtraction button on the calculator!!!'
 You must do the algorithm mentally and tell your partner the solution
before you press the 'equals' button.
 press 'equals' to confirm  reflect on the strategy you used if
you arrived at an incorrect answer.
Discuss the developing stages of computations  use of fingers  use
of strategies  automacy  i.e. 'See it, Say it'
 Fingers work for starters but are a slow inefficient strategy.
 Why might it be important to achieve 'automacy'?
 Where are you at as a learner?
 I know that under stress I revert back to what I'm sure of. Discuss.
 Walk the room checking the tasks are being done  stand a short
while behind the pair that you 'suspect'  you know the ones I mean
:)
 Ask  'What numeral is in Tens of Thousands, Thousands, Hundreds,
Tens, Units column?
 Ensure the students are verbalising their thinking.
 Zero is a numeral  the letter O is a letter  insist on mathematical
vocabulary.
 What is the difference between a numeral and a number?
 Say 'Gee Gee' at the end of the game. It stands for 'Good Game'.
Developing
Number strategies
Play
the game over a week with different skill / strategy focuses:

only allowed to subtract 5
 only allowed to subtract 6 (5  1 more)
 only allowed to subtract 7 (5  2 more)
 only allowed to subtract 8 (10 + 2 more)
 only allowed to subtract 9 (10 + 1 more)

Colour in a hundreds grid to find the patterns.

Discuss 'Jumps to decades'

How can the 'Facts to Ten' help arrive at answers more quickly?
9+1, 8+2, 7+3, 6+4, 5=5, 4+6, 3+7, 2+8, 1+9

What strategy works for you?
Something
to reveal and explore after playing the game for a while :)

Here is a sequence of numbers that will help you win the game every
time if you start first.

91, 81, 71, 61, 51, 41, 31, 21, 11

What is the strategy or pattern? How will it help you win?