Copyright © University of Cambridge. All rights reserved.
'How Random!' printed from http://nrich.maths.org/
Full screen version
If you can see this message Flash may not be working in your browser
Please see http://nrich.maths.org/techhelp/#flash to enable it.
To get an idea of how this interactivity works, set the grid size
to 10 rows and 10 columns, and the size of each trial to 10.
Click on "Randomise" a few times. Can you work out what is
Clear the grid so that the red squares disappear.
Now click in the "Keep previous trials" box, still with the grid
size at 10 by 10 and the size of each trial at 10.
This time, click "Randomise" exactly ten times. What happens? Is
this what you expected?
Clear the grid once more and try the same thing again, clicking
"Randomise" exactly ten times with the "Keep previous trials" box
Can you explain what you think is happening? You may want to repeat
this several more times to test your ideas.
Clear the grid again and this time click on the "Toggle Shape Type"
button. You'll see a shape appear on the grid. Make sure the "Keep
previous trials" box is ticked again.
How many times do you think you'll have to click on "Randomise" in
order for all the small squares you can see to be coloured
Try it and find out. How close were you?
Try the same thing again. Were you closer this time? Why do you
think that was?
Once all the small squares you can see are red, how many small
squares hidden by the shape would you expect to be white still?
Remove the shape and see whether you were right.
How would your estimate for the number of white squares left depend
on the size of the shape?
You could choose some different shapes to try out your ideas.
This interactivity can be used to help estimate the area of a
shape. Can you explain how?