Math CentralQuandaries & Queries


Question from Cecelia, a student:

If I am a whole number less than 100
and the sum of my digits is 4
and half of me is an odd number
What number am I?
Also am I prime or composite?

If you are a positive integer less than 100 then you are a one or two digit number. The sum of your digits is 4 and thus if you are a one digit number you are 4. If you are a two digit number then your digits must be 0 and 4, 1 and 3 or 2 and 2. Write down all the possible numbers you can make with these digits and look for one that satisfies "half of me is an odd number".


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