It takes Richard Semmler 5 hours to prepare a Little League baseball field. It takes Larry Gilligan 6 hours to prepare the same field. How long will it take Richard and Larry working together to prepare a Little League baseball field?

Given: ae ≅ ce ; de ≅ be prove: abcd is a parallelogram. we have that ab || dc. by a similar argument used to prove that △aeb ≅ △ced, we can show that △ ≅ △ceb by. so, ∠cad ≅ ∠ by cpctc. therefore, ad || bc by the converse of the theorem. since both pair of opposite sides are parallel, quadrilateral abcd is a parallelogram.