Question : From the top of house A in a street, the angles of elevation and depression of the top and foot of another house B on the opposite side of the street are 60° and 45°, respectively. If the height of house A is 36 m, then what is the height of house B? (Your answer should be nearest to an integer.)
Option 1: 91 m
Option 2: 98 m
Option 3: 94 m
Option 4: 93 m
Correct Answer: 98 m
Solution :
Given, AP = 36m In $\triangle PAB$, $⇒ \tan45^\circ = \frac{PA}{AB}$ $⇒ 1 = \frac{36}{AB}$ $⇒ AB = 36$ m $⇒ AB = PR = 36$ m In $\triangle PQR$, $⇒ \tan60^\circ = \frac{QR}{PR}$ $⇒ \sqrt3 = \frac{QR}{36}$ $⇒ QR = 36 \sqrt3 = 36 × 1.732 = 62.35$ Now, $QB = QR + RB$ $⇒ QB = 62.35 + 36 = 98.35$ $⇒ QB \approx 98$ m Hence, the correct answer is 98 m.
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Question : Two points A and B are on the ground and on opposite sides of a tower. A is closer to the foot of the tower by 42 m than B. If the angles of elevation of the top of the tower, as observed from A and B are 60° and 45°, respectively, then the height of the tower is closest to:
Option 1: 87.6 m
Option 2: 98.6 m
Option 3: 88.2 m
Option 4: 99.4 m
Question : From a point 12 m above the water level, the angle of elevation of the top of a hill is 60° and the angle of depression of the base of the hill is 30°. What is the height (in m) of the hill?
Option 1: $48 \sqrt{3}$
Option 2: $36$
Option 3: $36 \sqrt{3}$
Option 4: $48$
Question : From the top of a lighthouse at a height of 20 metres above sea-level, the angle of depression of a ship is 30°. The distance of the ship from the foot of the lighthouse is:
Option 1: $20$ m
Option 2: $20 {\sqrt3}$ m
Option 3: $30$ m
Option 4: $30 {\sqrt3}$ 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: $\sqrt{3}$
Question : The angles of elevation of a pole from two points which are 75 m and 48 m away from its base are $\alpha$ and $\beta$, respectively. If $\alpha$ and $\beta$ are complementary, then the height of the tower is:
Option 1: 54.5 m
Option 2: 61.5 m
Option 3: 60 m
Option 4: 50 m
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