Question : Let A and B be two towers with the same base. From the midpoint of the line joining their feet, the angles of elevation of the tops of A and B are 30° and 60°, respectively. The ratio of the heights of B and A is:
Option 1: 1 : 3
Option 2: 3 : 1
Option 3: 1 : 2
Option 4: $1: \sqrt{3}$
Correct Answer: 3 : 1
Solution : There are two towers A and B The angles of elevation of the tops of A and B are 30° and 60°, respectively $\angle$ AOC = 30°, $\angle$ BOD = 60° OC = OD $\tan \theta = \frac{\text{Perpendicular}}{\text{Base}}$ Let AC = h Then, BD = H In triangle AOC, $\tan 30^\circ = \frac{\text{h}}{\text{OC}}$ $\frac{1}{\sqrt{3}} = \frac{\text{h}}{\text{OC}}$ -----(1) In triangle BOD, $\tan 60^\circ = \frac{\text{H}}{\text{OD}}$ $\frac{\sqrt{3}}{1} = \frac{\text{H}}{\text{OD}}$ -----(2) By Dividing eq (1) and eq (2) $\frac{1}{3} = \frac{\text{h}}{\text{H}}$ ⇒ H : h = 3 : 1 Then the ratio of the height of tower B to tower A = 3 : 1 Hence, the correct answer is 3 : 1.
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Question : Let A and B be two towers with the same base. From the midpoint of the line joining their feet, the angles of elevation of the tops of a and b are 30o and 45o, respectively. The ratio of the heights of A and B is:
Option 1: $1: 3$
Option 2: $1: \sqrt{3}$
Option 3: $\sqrt{3}: 1$
Option 4: $3: 1$
Question : If the angle of elevation of a balloon from two consecutive kilometre stones along a road are 30° and 60° respectively, then the height of the balloon above the ground will be:
Option 1: $\frac{\sqrt{3}}{2}$ km
Option 2: $\frac{1}{2}$ km
Option 3: $\frac{2}{\sqrt{3}}$ km
Option 4: $3\sqrt{3}$ km
Question : Two posts are 2 metres apart. Both posts are on the same side of a tree. If the angles of depressions of these posts when observed from the top of the tree are 45° and 60° respectively, then the height of the tree is:
Option 1: $(3-\sqrt{3})$ metres
Option 2: $(3+\sqrt{3})$ metres
Option 3: $(-3+\sqrt{3})$ metres
Option 4: $(3-\sqrt{2})$ metres
Question : If the angle of elevation of the Sun changes from 30° to 45°, the length of the shadow of a pillar decreases by 20 metres. The height of the pillar is:
Option 1: $20(\sqrt{3}-1)$ m
Option 2: $20(\sqrt{3}+1)$ m
Option 3: $10(\sqrt{3}-1)$ m
Option 4: $10(\sqrt{3}+1)$ m
Question : From an aeroplane just over a straight road, the angles of depression of two consecutive kilometre stones situated at opposite sides of the aeroplane were found to be 60° and 30°, respectively. The height (in km) of the aeroplane from the road at that instant, is:
Option 1: $\frac{\sqrt{3}}{2}$
Option 2: $\frac{\sqrt{3}}{3}$
Option 3: $\frac{\sqrt{3}}{4}$
Option 4: $\sqrt{3}$
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