Final answer:
The height of the water tower is 120 ft.
Step-by-step explanation:
To solve this problem, we can use similar triangles. We have a 3-ft stick and a 5.25-ft shadow, and a water tower with an unknown height and a 210-ft shadow. The ratio of the stick's height to its shadow is the same as the ratio of the water tower's height to its shadow. We can set up a proportion to find the height of the water tower:
3/5.25 = x/210
Cross multiplying, we get 5.25x = 3 * 210
Dividing both sides by 5.25, we find that x = 3 * 210 / 5.25 = 120 ft.
Therefore, the water tower is 120 ft tall. The correct answer is D. 120 ft.