math
posted by karin on .
if you are 6 ft tall and cast a 90" shadow and are standing 70" from a lamp how tall is the lamp
someone helped with this earlier (steve) but I still don't understand how you got your answer...can you please explain further?

draw a diagram. Two ratios are the same
lamp height:distance to shadow tip
person height:length of shadow
so,
x/160 = .8
x = 128