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From the top of a tower, the angles of depression of two objects A and B (situated on the ground on the same side of the tower) are observed to be 30° and 60°, respectively. If the distance between the objects is 200√3 m, then the height of the tower is?

Solution

✅ Correct Option: 4

Let height of tower = hh meters.

Since the angle of depression to object B is 60° and to object A is 30°, and 60° > 30°, object B is closer to the tower than object A.

The angle of depression from the tower equals the angle of elevation from the ground (alternate angles).

From object B, angle of elevation = 60°

From object A, angle of elevation = 30°


Let distance from tower base to object B = xx

Let distance from tower base to object A = yy

For object B:

tan⁡(60°)=hx\tan(60°) = \dfrac{h}{x}

3=hx\sqrt{3} = \dfrac{h}{x}

x=h3x = \dfrac{h}{\sqrt{3}}


For object A:

tan⁡(30°)=hy\tan(30°) = \dfrac{h}{y}

13=hy\dfrac{1}{\sqrt{3}} = \dfrac{h}{y}

y=h3y = h\sqrt{3}


Since B is closer and A is farther, the distance between them:

y−x=2003y - x = 200\sqrt{3}

h3−h3=2003h\sqrt{3} - \dfrac{h}{\sqrt{3}} = 200\sqrt{3}

h(3−13)=2003h\left(\sqrt{3} - \dfrac{1}{\sqrt{3}}\right) = 200\sqrt{3}

h(33−13)=2003h\left(\dfrac{3}{\sqrt{3}} - \dfrac{1}{\sqrt{3}}\right) = 200\sqrt{3}

h(23)=2003h\left(\dfrac{2}{\sqrt{3}}\right) = 200\sqrt{3}


h=2003×32h = 200\sqrt{3} \times \dfrac{\sqrt{3}}{2}

h=200×32h = \dfrac{200 \times 3}{2}

h=300h = 300 m

Therefore, the height of the tower is 300 m.

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