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Make a cube out of straws and have a go at this practical challenge.


Reasoning about the number of matches needed to build squares that share their sides.

Little Boxes

How many different cuboids can you make when you use four CDs or DVDs? How about using five, then six?

World of Tan 24 - Clocks

Age 7 to 11
Challenge Level

This activity follows on from World of Tan 23 - Transform This Into That.

It is the end of the week. The men have gone home and the children have returned from school and then gone out again with their friends. Mah Ling and Granma T are the only people left and they are busy 'doing the books'. It is late, and the first cold wind of November is blowing down the leaves.

Mah Ling: It's a lazy wind that's blowing under that door.

Granma T: What's that? I've never heard that phrase before.

Mah Ling: Oh, it's something that Leo and Leone taught me last year when they visited. The wind is so lazy - it blows through you and not round you.

Granma T: You're right, it feels like the wind is chilling my bones. But I am much older than you, Mah Ling, and I feel the cold more than I did as a younger woman.

Mah Ling: We're both getting older - it's amazing how time flies!

Granma T: Isn't that what Leo called "Tempus Fugit?"

Mah Ling: That's right! You know, it was a good idea to have those children from the International School to stay with us. Is anything happening this year?

Granma T: Little Ming and Little Fung went to visit Leo and Leone at their school in Hong Kong a few weeks ago. One day they hope to visit England with them.

Mah Ling: They're doing much more than I did when I was younger! I'd love to take the time to travel, to see another country, to see how other people live...

Granma T: Speaking of time, we must push on and finish those figures. I'll just write a quick note asking Wai Ping to put a strip over the gap at the bottom of the door, to block out the wind. We might as well have comfort as we get older...

In the meantime, complete the silhouette of the grandfather clock.

Extra activity:
  • Have a go at this problem, using 7-minute and 11-minute sand timers to time some pasta which needs to cook for 15 minutes. What other times can you measure with these sand timers?

The story continues in World of Tan 25 - Pentominoes.