How to play

DECIMAL GAME is an online game for exploring decimal numbers. First you estimate (a key skill with decimal numbers), then you measure a length between 0 and 15. On the start page you choose Level 1, Level 2, Level 3 or Playground mode. At each level a purple line shows a length between 0 and 15: at level 1 the length is a whole number, at level 2 it has one decimal place, at level 3 two decimal places.

LEVEL 1 – Whole units only

You start at level 1, where the length to estimate is a whole number. As the picture shows, a purple line marks the quantity to estimate, and you type your estimate in the box below.

The exercise builds familiarity with the idea of estimating: first you try to "guess" where the number is, then you use the buttons to add or remove units until you find the right measure. Once the length has been estimated, you measure it with the “add a unit” and “remove a unit” buttons.

In the game students are invited to rely on their Approximate Number System, the ability to estimate a quantity intuitively. The first aim of the activity is not an exact answer but learning to try without fear: through trial and error, perception gets sharper.

LEVEL 2 – Here come the tenths

When the class is confident estimating whole numbers, move on to Level 2. Now the line can stop “between” two units, because tenths come into play.

After the usual first estimate, students notice that the exact measure needs fractions of the unit: tenths.

With a little practice, estimates become surprisingly accurate.

LEVEL 3 – Accurate to the hundredth

At level 3, hundredths join units and tenths. Since hundredths are very small, even measuring is hard at this level. Still, the level helps the class sense that you can go on past tenths indefinitely, each time taking a tenth of the previous unit and getting ever more precise measures.

PLAYGROUND – Compare numbers

In Playground mode there is no length to estimate: players build their own numbers by adding units, tenths and hundredths. When they reach the value they want, they click SAVE to fix it on screen with a coloured line. This tool is useful for comparing two decimals. In the example in the picture, 4.2 (green) and 4.02 (light blue) have been saved: clearly 4.2 > 4.02.