there are 12 inches in 1foot
and there are 3feet in 1 yard
if the boy is 5'6", then 6" is half a foot, so the boy is 5.5ft tall
if the shadow of the pole is 2yards, then is 2*3ft, or 6ft
check the picture below
the triangles are similar by AA, thus using proportions, we get that much
how many "inches" in 16.5ft? well, 12 * 16.5
