



 
Brennen, A strange shape for a railway bridge. I would have said "A tunnel through a mountain is in the shape of a parabola ...". I put a coordinate system on the diagram with the Xaxis on the road surface and the Yaxis passing through the vertex of the parabola. The parabola then has its equation of the form $y = a x^2 + b.$ From the diagram, when $x = 0, y = 5$ and when $x = 3, y = 0.$ Use these facts to solve for $a$ and $b.$ (Since the parabola opens downward $a$ will be negative.) If the truck drives down the centre of the road then the side of the truck will be at $x = 1.$ What is the height of the tunnel at $x = 1?$ Penny  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 