A vet has weighed three of his cats - Tibbles, Nibbles and Scribbles. Tibbles and Nibbles together weigh 7kg. Nibbles and Scribbles together weigh 8kg and Tibbles and Scribbles together weigh 11kg. He challenges students to find the weight of each cat individually.

First broadcast:
14 September 2007

Pause the clip before the answer is revealed and ask the pupils how they would go about solving this problem. Introduce the idea of using symbols instead of numbers. Use the initial letter for each cat's name and explain that it is easier than writing out the names each time. Ask the pupils for possible combinations of Tibble's and Nibble's weight. Ask them to write their ideas down on mini white boards. Continue this with the other 2 pairs of cats and allow the pupils some time to work in small groups or pairs to come up with their answers. Show the end of the clip. Who got the answer correct?