Question 221845
When you draw the diagonal, you divide the 
rectangle into 2 right triangles which are
sharing the diagonal as a common side.
So what you need is the pythagorean theorem
{{{d^2 = w^2 + l^2}}}
{{{d^2 = 120^2 + 160^2}}}
{{{d^2 = 14400 + 25600}}}
{{{d^2 = 40000}}}
{{{d = sqrt(40000)}}}
{{{d = 200}}} ft