When the sun is 30° above the horizon, shadow of one tree is 17·3 m long. What is the height of this tree ?
20 m
17·30 m
10 m
1·73 m
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC NDA-1 – 2015
Given L = 17.3 m and tan(30°) = 1/$\sqrt{3}$.
H = L * tan(30°) = 17.3 m * (1/$\sqrt{3}$).
H $\approx$ 17.3 / 1.732.
Notice that 17.3 is very close to 10 * 1.73. If we assume the shadow length is precisely $10\sqrt{3}$ meters (which is approximately 17.32 m), then:
H = $(10\sqrt{3}) \times (1/\sqrt{3}) = 10$ meters.
Given the options, 10 m is the most likely intended answer, implying the shadow length 17.3 m was an approximation for $10\sqrt{3}$ m.