How many five-digit numbers are there for which each digit is either equal to both adjacent ones, or differs from its neighbors exactly by 1 (from one smaller by 1, and from the other larger by 1) and which contain the digit 5?

(1/x + 1)^2 + 6 (1/x + 1) +5

You have 2 sides that are 2 cms and you have 6 sides that are 1/2 cm and you have 4 sides that are 1 cm. the smallest sides are 1/2 the medium sized sides are 1 and the smallest are 1/2. so to find the perimeter you have to add them all up together so your answer will be 11 cm's