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MathNet 2020 — Math Olympiad Vault — Part 03 Question 100

Math Olympiad Vault · MathNet 2020 — Math Olympiad Vault — Part 03

Question 100

We write $99$ circles in a line and in their interior we write the numbers from $1$ to $99$, as follows:
Question illustration
We color each circle with one of the two colors: red (R) and green (G). We say that a coloring is «good», if the following happens:
The number of red circles in the first part of numbers from $1$ to $50$ is greater than the number of the red circles existing in the second part from number $51$ to $99$.

a. Determine how many different colorings can be constructed.

b. Determine how many different “good” colorings can be constructed.

(Note: Two colorings are different, if they have different colors at least in one circle.)