A certain shade of purple paint is created by mixing 4 pints of red paint with 7 pints of blue paint. How many pints of blue paint must be mixed with 20 pints of red paint?

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