All solutions were successfully tested on 18 April 2013.

**count_evens:**

def count_evens(nums): count = 0 for element in nums: if element % 2 == 0: count += 1 return count

**big_diff:**

def big_diff(nums): return max(nums) - min(nums)

**centered_average:**

def centered_average(nums): sum = 0 for element in nums: sum += element return (sum - min(nums) - max(nums)) / (len(nums)-2)

**sum13:**

def sum13(nums): if len(nums) == 0: return 0 for i in range(0, len(nums)): if nums[i] == 13: nums[i] = 0 if i+1 < len(nums): nums[i+1] = 0 return sum(nums)

**sum67:**

def sum67(nums): for i in range(0, len(nums)): if nums[i] == 6: nums[i] = 0 for j in range(i+1, len(nums)): temp = nums[j] nums[j] = 0 if temp == 7: i = j + 1 break return sum(nums)

Line 9 is not necessary. However, by adjusting “i” you ensure that this script runs in linear time, despite the nested loop.

**has22:**

def has22(nums): for i in range(0, len(nums)-1): #if nums[i] == 2 and nums[i+1] == 2: if nums[i:i+2] == [2,2]: return True return False

The second option is much nicer to look at, but either way is fine.