matilda's father bought and sold cars,and he seemed to make quite a lot of money from doing it.
'Sawdust; he said proudly. 'That's the secret. And it costs me nothing. I get it from the wood shop.'
'How can sawdust help you to sell cars,daddy?' asked Matilda. I don't understand.'
That's because you're a stupid little girl, her father said. He turned to his son. I'm always glad to buy a car with an old gearbox, one that makes a terrible noise. I get it cheap. Then I mix a little sawdust with the oil in the gearbox and it goes beautifully-for a day or two.
How long will it go like that before it starts making noises again? asked Matilda.