Have you considered drawing a sketch?
let x be the distance from the fence to the ladder base, so x+7 is the distance to the building from the ladder base.
x/6=(x+7)/h where height at the building intercept.
dx/6=dx/h-7/h^2 dh -x/h^2 dh
dx/dh (1/6-1/h)=-1/h^2 (7-x)
but dx/dh=0 so
x must 7
so length can be figured from
length=2(sqrt (16+49))
check that, I did it quickly.
A fence 6 feet tall runs parallel to a tall building at a distance of 7 feet from the building. What is the length of the shortest ladder that will reach from the ground over the fence to the wall of the building?
1 answer