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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!

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Can you explain the strategy for winning this game with any target?

### Counting Factors

Is there an efficient way to work out how many factors a large number has?

# How Old Are the Children?

##### Age 11 to 14Challenge Level

A student in a maths class was trying to get some information from her teacher.

 Sally : "How many chidren have you got, Mrs Smith?" Mrs Smith: "Three" Sally: "How old are they?" Mrs Smith: "If you multiply their ages together, it comes to 72" Sally: "That doesn't give us enough information, Mrs Smith" Mrs Smith: "If you add the ages you get the number of this room" Sally: "That still doesn't give us enough information, Mrs Smith" Mrs Smith: "The youngest is called Amanda" Sally: "Thank you. Now we know how old they are !"

Well, how old are they?