Perhaps if you work backwards, you can devise an answer? How many people are re-shingling the roof, and for how many days will they be working? How many of those days will you be having pancakes with said number of “shinglers”? Take the serving amount times the number of days and “shinglers” and add extra in case a visitor arrives during the process. As for the canoe losing a wheel, it would have gone faster than 2 mph without it, so no worries.
Sometimes the solution is not so difficult.