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Two persons are on diametrically opposite sides of a tower. They measure the angles of elevation of the top of the tower as 30° and 60° respectively. If the height of the tower is 100 m, what is the approximate distance between the two persons ?

This question was previously asked in
CDS 1 2026 Maths Question Paper (12-Apr-2026)
The correct answer is

230 m

To solve the given problem, we will use trigonometry. We need to find the approximate distance between two persons who are on diametrically opposite sides of a tower. The height of the tower is given as 100 meters, and the angles of elevation to the top of the tower from the two opposite sides are 30° and 60°, respectively.

Let's denote:

  • Height of the tower, \(h = 100 \text{ m}\)
  • Distance of person A from the base of the tower, \(d_1\), who sees the angle of elevation as 60°
  • Distance of person B from the base of the tower, \(d_2\), who sees the angle of elevation as 30°

Using the tangent function for person A, we have:

\(\tan(60^\circ) = \frac{h}{d_1}\)

\(\sqrt{3} = \frac{100}{d_1}\)

\(d_1 = \frac{100}{\sqrt{3}}\)

Rationalizing the denominator:

\(d_1 = \frac{100\sqrt{3}}{3}\)

Using the tangent function for person B, we have:

\(\tan(30^\circ) = \frac{h}{d_2}\)

\(\frac{1}{\sqrt{3}} = \frac{100}{d_2}\)

\(d_2 = 100\sqrt{3}\)

Since the persons are on diametrically opposite sides of the tower, the total distance between them is given by:

\(d_1 + d_2 = \frac{100\sqrt{3}}{3} + 100\sqrt{3}\)

To calculate this, we will bring both terms to a common base:

\(d_1 + d_2 = \frac{100\sqrt{3}}{3} + \frac{300\sqrt{3}}{3}\)

\(d_1 + d_2 = \frac{400\sqrt{3}}{3}\)

Using the approximate value of \(\sqrt{3} \approx 1.732\), we calculate:

\(d_1 + d_2 \approx \frac{400 \times 1.732}{3}\)

\(d_1 + d_2 \approx \frac{692.8}{3}\)

\(d_1 + d_2 \approx 230.9 \text{ m}\)

Hence, the approximate distance between the two persons is 230 m, which matches the given option.

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Important Questions from Heights and Distances

  1. Two ships are sailing in the sea on the two sides of a lighthouse. The angles of elevation of the top of the lighthouse as observed from the ships are 45 ° and 60° respectively. If the lighthouse is 81 m high, then the distance between two ships is:

  2. The horizontal distance between two towers is 40√3 m. The angle of depression of the top of the first tower when seen from the top of the second tower is 30°. If the height of the second tower is 130 m, find the height of the first tower.

  3. The angle of elevation of a ladder leaning against a house is 60° and the foot of the ladder is 6.5 metres from the house. The length of the ladder is

  4. A kite is flying at a height of 50 m. If the length of the string is 100 m then the inclination of the string to the horizontal ground in degree measures is:

    A. 90

    B. 45

    C. 60

    D. 30

  5. Two poles of the height 15 m and 20 m stand vertically upright on a plane ground. If the distance between their feet is 12 m, find the distance between their tops.

    A. 11 m

    B. 12 m

    C. 13 m

    D. 14 m

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