Coin tossing simulation to get x heads in a row, ten times - timely at higher amount of heads
Fails if they don't enter an integer
You are doing integer math on the average
I would prefer ++; over += 1;
I would rather see a foreach
Odd but rnd.Next(2) is faster
Need to get into the millions for a decent sample  

public static void CoinToss()
{
    int sample = 1000000;
    Debug.WriteLine($"Enter a head streak to achieve. This will be executed {sample.ToString("N0")} times to generate an average.");
    int desiredStreak = 10;  
    int grandTotalAttempts = 0;
    int currentStreak;
    int totalAttempts;
    Random rnd = new Random();            
    for (int i = 0; i &lt; sample; i++)
    {
        currentStreak = 0;
        totalAttempts = 0;
        while (currentStreak != desiredStreak)
        {
            if (rnd.Next(2) == 0)
            {
                currentStreak ++;
            }
            else
            {
                currentStreak = 0;
            }
            totalAttempts ++;
        }
        if ((i + 1) % (sample / 20) == 0)
        {
            Debug.WriteLine($"Attempt Number: {(i + 1).ToString("N0")}");
            Debug.WriteLine($"Total Attempts: {totalAttempts.ToString("N0")}");
            Debug.WriteLine("");
        }
        grandTotalAttempts += totalAttempts;  
    }
    Debug.WriteLine($"Average Attempts: {((decimal)grandTotalAttempts / sample).ToString("N2")}");
}