Kaitlin is participating in a 5-day cross country biking challenge. she biked for 55,67,56,and 49 miles on the first four days. how many miles does she need to bike on the last day so that her average (mean) is 55 miles per day?

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.