geometrY
posted by shannon .
to estimate the height of a tree, Dave stands in the shadow of the tree so that his shadow and the tree's shadow end at the same point. Dave is 6 feet 4 inches tall and his shadow is 15 feet long. If he is standing 66 feet away from the tree, what is the height of this tree?

http://member.tripod.com/~BDaugherty/GCSEMaths/shapes.html
See the last picture at the bottom of this web page (for a pic of this exact problem).
Using ratios,
Tree height = T
15/66 = 6.33/T
15T = 512.73
T = 34.182
T = 34.182 
I think you did something wrong