B. 8 ft
Solution:
The basic proportionality theorem states that if a line is drawn parallel to one side of a triangle and it intersects the other two sides at two distinct points then it divides the two sides in the same ratio.
In the above-shown figure, DE is the height of one tree, AB is the height of another tree. AB⊥AC and DE⊥AC, therefore, AB∣∣DE
As shown in the above figure, let AB=x, CD=12.5 ft, CA=20 ft and DE=5 ft.
Using the basic proportionality theorem, we have
CD = DE
CA = AB
⇒ 12.5 = 5
20 x
⇒ 12.5x= 20 × 5
⇒ 12.5x= 5
⇒ x = 100 = 8
12.5
Hope it helps u U^ｪ^U
