Calculator Slido
Years 3 - 7

A calculator challenge for one or two players.


When a card is face down on the board it means zero (0).
The cards in the photo show 700.


  • One calculator (there's one on your phone)
  • Print this set of Operation Cards and cut into separate cards.
    - For one person just cut the first two rows.
  • Fold a piece of A4 paper in half shortways, then again to get four sections. Repeat for a second piece of paper and sticky tape them together to make eight (8) sections.
    - The photo shows lines where the sections are.
    - If you press hard when you fold you won't need to draw lines.
    - Write place value headings at the top of the columns.
    - Start with 1 in the far right column, then go to the left writing
      10 ... 100 ... 1000 ... 10,000 ... 100,000 ... 1,000,000
      as the headings.
  • Take a set of cards 1 - 9 from a card pack.
  • Keep the rest of the pack face down on the right side of the board. They will be used as zeros.
  • Write the title of this challenge and today's date on a fresh page in your maths journal.
The zeros tell us that seven hundred (700) has no tens and no ones. It just has 7 hundreds.
  • Choose your own three digit number and make it with the cards.
  • Write it in your journal and also write it in place value words. Example: 492 - 4 hundreds, 9 tens and 2 ones.
  • Do this for three more three digit numbers, but one them must have one zero in it.
  • Do it for a 4 digit number, ...a 5 digit number, ...a 6 digit number, ...a 7 digit number.

Exploring Calculator Slido

Calculator Slido can be played as a two person game, but we will explore it first.
You can explore it by yourself or with your partner.

In this game you move your three digit number left or right using the Operation Cards.

Making Numbers Bigger and Smaller

  • When a number is made 10 times bigger all its digits move together one column to the left.
  • If there is an empty space left behind, a face down card slides off the pack to show there is zero here in the new number.
  • When a number is made 10 times smaller all its digits move together one column to the right.
  • If a zero isn't needed it is pushed back to the pack.
  • When it's 100 times, the movement is two columns.
  • When it's 1000 times the movement is three columns.
How to Play
We will start with 700.
Put it on your board and write that number on your calculator.
  1. Shuffle the Operation Cards and place them face down.
  2. Pick up an Operation Card and slide the 700 the way the card tells you.
  3. Check that zeros are used to save places if it gets bigger, or removed from saving places if it gets smaller.
  4. Say the new number.
  5. Multiply (times bigger) or divide (times smaller) on the calculator using the Operation Card.
    The calculator and the board should now both show the same number.
  6. Pick up a new Operation Card and repeat.
  7. Play continues until the first digit - seven (7) in this case - slides exactly into the Millions column.
    Start the game over with a new number on the board when this happens.
  8. If an Operation Card would cause the number to move beyond the Millions or beyond the Ones put it back and take the next one.

Have fun exploring Calculator Slido.

Two Players

  • Play the same way, but take turns picking up the Operation Cards.
  • When you say the new number you get one point for saying it correctly.
  • If an Operation Card would cause the number to move beyond the Millions or beyond the Ones miss a turn.
  • The winner is the person who gets the first digit of the number exactly into the Millions column.
  • Two points for doing that.
  • Play five games and the person with the higher score wins.

Doing It With Decimals

Decimals are parts, or fractions, of one whole that follow the pattern tenths, hundredths, thousands,.... That means that they belong with the 10 times bigger and 10 times smaller numbers and can join in this game.
  • Make another playing board with three sheets of paper, but cut off one section so there are only eleven (11) sections.
  • We use words for column headings this time.
    - Write Ones at the top of the middle column and put a decimal point right there beside it.
    - To the left put headings: Tens, Hundreds, Thousands...
    - To the right put headings: Tenths, Hundredths, Thousandths...
  • To start put down three cards side by side, but one of them must be in the ones column.
  • Remember to say every new number you make and write it on the calculator like before.
  • The face down cards sit under the ones column.
  • Play the same way as before with the aim of being the person who gets the first digit into the Hundred Thousands column.
  • Or you can play with the aim of being the person who gets the last digit into the Hundred Thousandths column.
The new thing is that if all the digits slide to the right passed the ones column you will have to slide zeros out to save places on that side of the decimal point too.
Have you noticed that:
  1. The decimal point hasn't moved. It never does. It stays in the ones column to separate the ten times bigger numbers from the ten times smaller numbers.
  2. We don't add zeros or take away zeros anywhere. We slide them in to show that there is zero of that column value in the new number.

Just Before You Finish

Answer this question in your maths journal.
  • What do you know now that you didn't know when you started Calculator Slido?


Answers & Discussion

Send any comments or photos about this activity and we can start a gallery here.


Maths At Home is a division of Mathematics Centre