# 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

**What You Need:**

– 1 calculator

– 2 players

**How to Play: **

** ****Part One
**

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

– 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

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