```
public double FindMaxAverage(int[] nums, int k)
{
int currsum = 0;
for(int i=0; i<k; i++)
{
currsum += nums[i];
}
int maxsum = currsum;
int start = 0;
int end = k - 1;
while(end<nums.Length-1)
{
currsum -= nums[start];
currsum += nums[end + 1];
maxsum = Math.Max(maxsum, currsum);
start++; end++;
}
return maxsum / (double)k;
}
```