4 red blocks and 3 blue blocks are arranged at random in a circle. What is the probability that no two blue blocks are side by side?

4 red blocks and 3 blue blocks are arranged at random in a circle. What is the probability that no two blue blocks are side by side?
Answer:
We take r = 3 and s = 4.
According to theory of runs
Total number of ways = r+s C r
= 7C3
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