Car number four cost eighty-six pounds and sold for six hundred and ninety-nine pounds fifty. Car number five cost six hundred and thirty-seven pounds and sold for sixteen hundred and forty-nine pounds and fifty pence. Did you write all that down?
`Yes, daddy' said the ten-year-old boy.
`Right, now tell me this,' said Mr Wormwood. `How much money did I make on each of the five cars, and how much money did your clever father make today?'
`That's difficult,' said the boy.
`I had an answer in ten minutes,' said her father.