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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

This problem is designed to intrigue a little. To tackle the problem, pupils will need to be comfortable with manipulating fractions and decimals, and it would be a good idea to have calculators to hand.

It is an excellent way to highlight misconceptions associated with our digital clock, for example that 12.50 is not 0.5 hours after 12.00. It could be a good vehicle for investigating why our clock is based on the number 60 and researching calendar systems of ancient cultures.