Agoldsmith combined an alloy that costs $4.20 per ounce with an alloy that costs $1.70 per ounce. how many ounces of each were used to make a mixture of 200 oz costing $2.25 per ounce?

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.