Translation:The telephone has a width of eight centimeters.
yes, that's exactly what i was going to ask. I don't know what your mother-tongue is, but I amj not a native english speaker and this is the sort of sentences which are not easy to translate because I have to think in three languages at the same time. I have translated it exactly like you say and DUO said it is wrong.. As a matter of fact it is NOT wrong. It is only that my translation is not a literal one. I very much doubt that any native english -speaker would say what DUO says. So your translation and mine should also be accepted I always remember my Latin professor telling us: please don't give me a literal translation. I know you know the vocabulary !