Question 44092
draw a line between the furthest corners. you now have a right-triangle with two adjacent sides with length a=7 and b=4
use Pythagoras' theorem {{{a^2+b^2=c^2}}} 
to give {{{c=sqrt(7^2+4^2)}}}
{{{c=sqrt(49+16)}}}
{{{c=sqrt(65)ft}}}

I hope this helps 
P.S. I am trying to start up my own homework help website. I would be extremely grateful if you would e-mail me some feedback on the help you received to adam.chapman@student.manchester.ac.uk