Math CentralQuandaries & Queries


Question from Will, a parent:

This is a math puzzle called "What's my number"
1. It is a three-digit whole number.
2. It is a square number.
3. It is divisible by 5.
4. it is not an even number.
5.Each of it digit is not different.
6. It is divisible by 9.
7.It is less than 500.
8. Its ones digit is 5.
9.It has only one odd digit.
10. Its tens digit is less than its ones digit.

Hi Will,

Clue number 2 and clue number 8 really allow us to make a short list of possibilities. Make a list of 3-digit square numbers that end in five and then see which of them match the other clues.

By the way, a "square number" is formed by multiplying a number by itself.
Also, in order to end in a 5, at least one of its factors must end in a five.

Hope this helps,

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