The answer is 13 you have to add the top and bottom
Here are a few doubles facts:
5+5=10
2+2=4
3+3=6
A double is simply a pair of identical numbers added together. There's a pair of doubles you can <em>subtract </em>1 from to get 6+7, and there's a pair you can <em>add</em> 1 to get the same answer. What are those pairs?
Hint: If you take the example 3+4, you can either <em>subtract 1</em> from the double 4+4 or <em>add 1</em> to the double 3+3 to obtain your answer.
The radius is 8
Im not sure if this is what your looking for
