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.
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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?