Hands-On Math Hundreds Chart

I wish there was a way to uncover a number without clearing the entire board. If you make a mistake you need to start over.

Works well, however there should be a way to erase just one number without erasing all the numbers on the chart. Sometimes you just touch a number by mistake but with this current program set up you have to erase all the numbers you have been working with in ordered to get that "one" erased.

Seems to have an arbitrary limit on the number of markers that can be placed -- so it's difficult to demonstrate the Sieve of Eratosthenes using a different color for each multiple of the first few primes. Also, removing a marker is difficult and haphazard. An undo button would be useful in addition to the eraser button which clears ALL of your work. Overall, a very handy app for teachers. I'm grateful.