



 
Khan, I put the important information on a diagram.
Since the vertex of the parabola (0, 0) is on the roadway at the centre of the span the point at the top of the tower has coordinates (343, 152). Thus the point (343, 152) is on the curve so substitute the coordinates of this point into x^{2} = 4ay and solve for a. Actually the cables in a suspension bridge do not have a parabolic shape but the curve is very close to a parabola. It is a curve called a catenary. Penny  


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