Sharp Logic

It's boring, driving to Melbourne, says Terence.

It depends on your outlook, says Katherine.

I don't have an outlook, says Terence. Can I sit in the front?

No, says Margaret, who is driving.

We're nearly there, says Katherine. Would you like another puzzle?

Only if there's a prize, says Terence.

Okay, says Katherine. Try this one. It's a logic puzzle. And if you get it right, you might win a prize.

We don't have a prize, says Margaret.

We could come up with something, says Katherine.

She hands Terence a picture puzzle.

Five red apples. Three whole ones and two with a quarter cut out. An empty box, for the answer. How many?

Use your pencil, says Katherine. Think about the answer. It could be tricky.

Terence looks at the apples.

Jinjing looks too.

There is a very long silence, long enough for Margaret to arrive in Ballarat, slow down, stop and change drivers. Now Katherine is driving.

Have you worked out the puzzle yet? asks Katherine.

Silence from the back seat. Margaret turns.

We can't agree, says Jinjing.

No prize then, says Margaret.

Five, says Terence.

Four and a half, says Jinjing.

Let me see, says Margaret. Hmm. Yes, it's not really obvious. An apple with a quarter cut out is still an apple.

Is it? says Katherine. At what point after cutting out segments does it stop being an apple?

It never stops being an apple, says Margaret.

An apple is not the same as a slice of an apple, says Katherine. Think Margaret. You have one apple. You cut out a segment. By your logic, you now have two apples.

Two pieces of apple, says Margaret.

So I win, says Terence.

Katherine would say so, says Margaret. But I would side with Jinjing.

No, you wouldn't says Katherine. Your logic would compel you to answer ...err... seven.

Nonsense, dear, says Margaret. The two missing quarters have not been depicted.

You are compelled to infer them, says Katherine.

What do I get? asks Terence.

Katherine thinks. She had been going to suggest a turn with Margaret's geology hammer. But that is now out of question.

Would you like to take charge of my cheese knife? says Katherine.

YES! says Terence. Is it sharp?

Sharp enough, says Katherine.