Today at Mathsclub, the children estimated the thickness of a piece of tissue paper by folding it 8 times (there was much discussion about whether 9 times was possible) and measuring the thickness of the 256 layers.

We also tackled the rice and chessboard problem (also known as the wheat and chessboard problem) and whether my jar of rice would be enough. Each child counted the grains in a teaspoonful of rice and we found the average (5ml contains about 250 grains). We worked out that there are about 50 million grains of rice in 1cubic metre. which we had reached by the 27th square. By square 47 rice 1 m deep covering 1 square kilometre is needed. The total amount is enough rice to cover all of China with a layer 3.8km deep, or to cover the whole earth with a layer just less than a millimetre thick – just a sprinkling!

According to Wikipedia, these days would take ten years rice production to find enough rice!