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

since 6' = 72 inches, if the lamp is x inches tall,
x/(70+90) = 72/90
x = 128 
can you further explain the part where you stated...
x/(70+90)=72/90
when I take 72/90 I get .8
I must be missing something here... 
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