Asurveyor needs to measure the distance, ab, across the lake. beginning at e, he locates the midpoint, c, of ae and the midpoint, d, of be. he then measures cd. what is ab?

Since C is the midpoint of AE and D is the midpoint of BE, that simply means CD is the "mid-segment" of the triangle, and the parallel base of AB is simply twice as long as CD.  Bearing in mind that the midsegment is half of the parallel base.

It will cost $540i think