Calculator Slido Calculator Activities    blackdouglas.com.au

There is no such thing as 'moving the decimal point'. The decimal point never moves. It is always in the Ones column as a marker to separate wholes from parts. No, it is not in a column of its own either. If it was there would be no symmetry in our numeral system.

Turn on a calculator. In 98% of cases the number you see is 0. not just 0. Programmers of these machines know that the decimal point is connected to, in the same column as, the Ones digit.

Calculator Slido is a game designed to encouraged children to see what really happens. When you multiply or divide by multiples of 10 the digits, as a block, slide left or right the necessary number of columns.

• Multiply by 10 and the digits slide one column to the left.
• Divide by 10 and the digits slide one column to the right.
• Multiply by 100 and the digits slide two columns to the left.
• Divide by 100 and the digits slide two columns to the right.

Zeros as used to fill the empty places and the decimal point hasn't moved. It is still the Ones Column as a marker separating wholes from parts.

Materials

• One calculator per group.
• One pack of Operation Cards per group.
• One pack of Digit Cards per group. If you want children to use numbers with repeated digits (622, 343 ...) you will need multiple packs of Digit Cards per group. Playing cards work well.
• Two pieces of scrap A4 paper and a marker per group.

Procedure

It is useful to model this game with a 'group in a fishbowl' before asking children to do it for themselves.

1. Students fold the two pieces of paper into four, mark column headings and use the Digit Cards to place any hundreds number as shown. (The back of playing cards can represent zero.) This is also the starting number written on the calculator.

2. Shuffle the Operation Cards and place them face down.
3. Player A picks up an Operation Card and makes the digit slide the appropriate amount on both the calculator and the playing board by doing what the card says.
4. Check that empty places on the playing board are held correctly with zeros.
5. Player A says the new number and if correct gains one point. If they say it incorrectly, they lose a point.
6. Players B, C, ... continue the game in the same way.
7. Play continues until one player slides the digit into the Millions column and gains two points for doing so. Start the game over when this happens.
8. If an Operation Card would cause the digit to move beyond the Millions or beyond the Ones that player misses a turn.
9. Play to either reach a total of points agreed in advance, or for a set time. In either case the player with the highest score wins.

Variations

• Start with any type of hundreds number, eg: 234, 240, 204
• Extend the playing board to the left and right to include higher numbers and/or decimals

• Return to
  • Calculator Activities index
• Return to:
  • Resources index
• Return to
  • Welcome page