A lightbulb emits light that creates a shadow of a ball on a wall. If the radius of the ball is 12.1 cm, and the radius of the shadow is 25.5 cm, and the ball is 2.09 m away from the wall, how far is the lightbulb away from the wall?
r= 12.1 cm, R= 25.5 cm, d=209 cm, x=?
R/x=r/(x-d)
r•x=R•(x-d)
x=R•d/(R-r) =
25.5•209/13/4 = 398 cm=
=3.98 m