I take it that we are to assume that the ratio between the actual length and the shadow length are directly proportional
so therefor we set up the following proprtion
actual height: shadow height=40ft:16ft
we are given that the tree is actually 27ft
so
40ft:16ft=27ft:?ft
make into a fraction
40ft/16ft=27ft/?ft
cross multiply or multiply both sides by 16?ft²
40?ft²=432ft²
divide both sides by 40ft
?ft=10.8ft
the length of the shadow is therfore 10.8ft