AoPS Wiki talk:Problem of the Day/June 15, 2011

Solution

We can solve this problem by a bit of trial and error. We can guess she rode days and we get since the mean is clearly and there are terms. That's a bit too small. We can add to and get . That's still to small. Now, we add to get , the answer we want. We now count how many numbers are in the following list: . Adding to the list gives us . Dividing by gives us . Subtracting gives us . Our list has numbers. Since she started on a Monday, we must add days. Our answer is