if you multiply by a factor of 16 to convert a larger unit of measurement to a smaller unit, by what factor would you multiply to convert the smaller unit of measurement to the larger unit? Explain your reasoning. 5th grade math

The perimeter of ? cde is 55 cm. a rhombus dmfn is inscribed in this triangle so that vertices m, f, and n lie on the sides cd , ce , and de respectively. find cd and de if cf=8 cm and ef=12 cm. the answer is not cd=20 and de=15. i have tried that one, it does not work.