Original source: http://www.mathmaniacs.org/lessons/01-binary/Binary_Piano/ This page
includes the following information:
The following craft is a simple method for helping children understand place value and
binary numbers. The idea is from Martin Beberman.
Below are two images. They should be copied back-to-back as exactly as possible, so
that the bold 0's on the back fall directly behind the powers of 2.
David Muir (firstname.lastname@example.org) created this Word document in April 2001. If
photocopied back to back, the two images should line up correctly.