The shadow length of the high benchmark of 1m is 0.5m, which means that the shadow length is half of the benchmark.

So when the shadow of a tree on the ground is 3 meters, it means that the corresponding tree is 6 meters, plus 2 meters parallel to the wall. The height of this big tree is 6+2 = 8 meters.

Enumerable proportion:

Let the part of the tree cast on the ground be x meters.

X:3= 1:0.5