# Calculator WipeOut – Number Sense Game

Free Calculator Game – Wipeout is a classroom favorite for teaching & experimenting with place value. It is an ideal warm-up activity.

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# Calculator Game

### Number Sense WipeOut Calculator Game – WipeOut – a Place Value Game

– 1 calculator
– 2 players

### How to Play:

Part One

1. Enter any five or six-digit number into the calculator e.g. 23 458
2. P1 asks P2 to subtracts a number on the calculator that will leave a zero in the Thousand’s column.
3. P2 asks P1 to subtract a number that will leave a 1 in the Hundred’s column & then read that number aloud.
4. P1 asks P2 to ‘wipe out’ the number in the Ten’s column to leave a zero & then read that number aloud.
5. P2 asks P1 to ‘wipe out’ the number in the Unit’s column so that it is replaced by zero.
6. P1 invites P2 to subtract a number that will leave only the number 100 visible on the calculator display.

### How to Play:

Part Two

– Take turns to subtract a number between 1 and 9 inclusive from the number displayed.
– The person who avoids making the calculator display zero is the winner.

### 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 – automaticity – i.e. ‘See it, Say it’
– Fingers work for starters but are a slow inefficient strategy.
– Why might it be important to achieve ‘ automaticity’?
– 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 verbalizing their thinking.
– Zero is a numeral – the letter O is a letter – insist students use
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)
– Color in a hundreds grid to find the patterns.
– 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

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