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Adding All Nine

Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!

Largest Product

Which set of numbers that add to 10 have the largest product?

Round and Round and Round

Where will the point stop after it has turned through 30 000 degrees? I took out my calculator and typed 30 000 ÷ 360. How did this help?

Decimal Time

Age 11 to 14
Challenge Level
What does the word "decimal" make you think of? You could try looking it up in a dictionary.
How many hours are there in one of our days? What time is it half way through our day?
So, what time is it half way through the French decimal day? What does this tell you about the total number of hours in the French decimal day?
Do both systems have the same number of minutes in an hour?