If the house on a particular stretch of road are all the old numbers starting at 11, how many houses are there if the total all the numbers is 551?
assuming consecutive numbers, we have n houses if
n/2 (2*11+(n-1)*1) = 551
n = Hmmm, not an integer
How about a typo, and you meant "odd" numbers. Then we gate
n/2 (2*11+(n-1)*2) = 551
Then n=19