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What Is the Question?
Age 11 to 16
Challenge Level 
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The answer is 49.
What is the question?
Why does it work?
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The answer is 42.
What is the question?
Why does it work?
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The answer is 63.
What is the question?
Why does it work?
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The answer is 56.
What is the question?
Why does it work?
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Does this always work?
Can you extend the method to other numbers?
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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!
Double Digit
Choose two digits and arrange them to make two double-digit numbers. Now add your double-digit numbers. Now add your single digit numbers. Divide your double-digit answer by your single-digit answer. Try lots of examples. What happens? Can you explain it?
