Some numbers are happy and others are not!
To find out whether a number is happy, square each of its digits, add the answers and repeat. If you end up with 1 the number is happy!
How many happy numbers can you find?
E.g. Consider 19
1^{2} + 9^{2} = 82
8^{2} + 2^{2} = 68
6^{2} + 8^{2} = 100
1^{2} + 0^{2} + 0^{2} = 1
This shows that 19 is a happy number.
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Topics: Starter  Arithmetic  Investigations
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access to computers? 

Here a concise URL for a version of this page without the comments.
Transum.org/go/?Start=January25
Here is the URL which will take them to an interactive Happy Numbers activity.