# Don't Let It Go Away!

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A $$6\times 4$$ grid contains $$24$$ small squares each of side length $$5$$. A coin of diameter $$4$$ is thrown on the grid such that it does not cross the outer boundary. The probability that the coin stays inside a small square, that is, doesn't cross an inner boundary line can be represented as $$\dfrac{a}{b}$$ where $$\gcd(a,b)=1$$. Find $$a+b$$.

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