At a particular time, objects and their shadows are proportionate.
Therefore, in figure,
--- (1)
where AB is the height of the lighthouse, BC, its shadow and FD is the height of Zara and DE is her shadow.
From the given information,
BC = 36 feet
FD = 4 feet and DE = 3 feet
(1) becomes
AB = 48
Hence, the height of the lighthouse is 48 feet.
