A number and a quarter of that number add up to fifteen. What is the number? To work out the answer the presenter uses a tile split into four equal parts. Using simple addition, division, multiplication and a degree of logic, he shows how it is possible to work out the answer.
The clip could be stopped after about 30 seconds to allow children to consider the problem. Between 30 and 45 seconds children could get another clue so there is a change stop and they can try again. This is then followed by the solution. Children might like to investigate 'Egyptian fractions' further. The Egyptians only used unitary fractions eg 1/3 or 1/4. They would not write 3/4 or 2/3 but instead they would express these fractions as the sum of different unitary fractions. For example 3/4 would be written as 1/2 + 1/4 or 2/3 could be written as 1/3 + 1/6. Ask children to explore different ways that fractions could be expressed. Who can come up with the longest chain? An example could be 2/3 = 1/3 +1/6+1/12+1/20+ 1/30.