given distance between tops of poles= 12m
the poles of heights 6m &11m ,difference lengths of poles= 5m
draw the line to longer pole form the top of shorter pole perdicularly and also join the tops of poles,clearly a right angled triangle is formed.
let the distance between their tops be xm
by pythagorus theorem x²=12²+5²=144+25=169
the value of x is 13,therefore distance between their tops is 13m