h(a+b)/2
not times 2
average base times height, common sense
For a trapezoid, the following formula relates the area A, the two bases a and b, and the height h.
A=(a+b)2hA=(a+b)2h
Solve for a.
a=2Ah+ba=2Ah+b
a=2A−bha=2A−bh
a=2Ah−ba=2Ah−b
a=Ah2−b
2 answers
A = h (a+b)/2
2 A/h = a + b
a = 2A/h - b
2 A/h = a + b
a = 2A/h - b