Make a 'Counting and Adding Machine' using a cardboard box!
Although not a classroom activity, this idea is still very good. A Puzzle Display is a display board, on which there are lots of puzzles, which children can try to work out during spare moments, or at break / lunch times. They are easy to make, and all you have to do is collect lots of different (mathematical or otherwise) puzzles and then pin them onto the board. A lot of these puzzles can be found on the net, and some examples / relevant links are shown below.
Instructions for making A Puzzle Display:
1) You will obviously need a blank display / wall on which you can put your puzzles.
2) You will also need LOTS of different puzzles to put onto the board. Some of these might include:
Rebus puzzles - Look at this page for plenty of examples.
Mathematical questions - these can consist of:
Arithmetic questions, e.g. What is 20 + 25?
Mathematical problems, e.g. If you begin with a one digit number, multiply by 3, add 8, divide by 2 and subtract 6, you will get the number back. Find the number.
Mathematical investigations - This Bingo investigation may be a useful starting point.
Optical Illusions, e.g. What can you see in the two pictures below?
Thanks to Michael Black for these Illusion pictures.
If the puzzle display is going to be in a classroom, the puzzles can be specifically suited to that classes' level of mathematical ability. If it is going elsewhere in the school (where all children are likely to see it) the level of the puzzles will obviously have to be over a greater range. You might want to include separate areas which have puzzles for children of different ages.
3) You can also include an area on which children can post their own puzzles for their friends to work out.
4) To keep the children's interest, change the puzzles regularly (perhaps weekly) and include an area which shows last week's answers.
5) You could include a "competition puzzle" on the board, so that the child who completes one of the puzzles first wins a prize. The winner's name could be written on a special "Winners List" on the display (along with the date).
6) This activity can also be used as the stimulus for a classroom activity. For example, ask your class to make lots of puzzles which they can put onto the display. This will save you time in finding puzzles. They could also search through Maths books to look for puzzles which might be appropriate.