Rays of sunlight are parallel.
So, ∆PQR and ∆ABC are equiangular i.e., similar triangles.
Sides of similar triangles are proportional.
∴ QR/BC = PR/AC
∴ Height of the tree (QR) = (BC/AC) x PR
Substituting the values of PR, BC and AC in the above equation, we can get length of QR i.e., the height of the tree.