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Question

A ladder 28 meters long leans against a wall, making an angle of 60° with the ground. Find the height at which the ladder touches the wall. (Use $\sqrt{3} = 1.74$)

The correct answer is
24.36 m

Ladder Height Calculation Using Trigonometry

This problem involves a right-angled triangle formed by the ladder, the wall, and the ground. We are given the ladder's length (hypotenuse) and the angle it makes with the ground. We need to find the height it reaches on the wall (opposite side).

Identify Given Information

  • Ladder Length (Hypotenuse): $L = 28$ m
  • Angle with Ground: $\theta = 60°$
  • Goal: Find the height on the wall (Opposite Side): $h$

Apply Trigonometric Relation

The sine function connects the angle, the opposite side (height), and the hypotenuse (ladder length):

$ \sin(\theta) = \frac{\text{Opposite}}{\text{Hypotenuse}} $

Substitute the known values:

$ \sin(60°) = \frac{h}{28} $

Solve for Height (h)

Rearrange the equation to find '$h$':

$ h = 28 \times \sin(60°) $

Recall that $\sin(60°) = \frac{\sqrt{3}}{2}$.

$ h = 28 \times \frac{\sqrt{3}}{2} $

Simplify:

$ h = 14 \times \sqrt{3} $

Calculate the Final Value

Use the given approximation $\sqrt{3} \approx 1.74$:

$ h = 14 \times 1.74 $

$ h = 24.36 \text{ m} $

Result

The height at which the ladder touches the wall is 24.36 m.

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Important Questions from Heights and Distances

  1. If x is the distance of P from the bottom of the pillar, then consider the following statements :

    1. x can take two values which are in the ratio 1 : 3

    2. x can be equal to the height of the flagstaff

    Which of the statements given above is/are correct?

  2. What is a possible value of tan θ ? 

  3. A vertical tower standing on a levelled field is mounted with a vertical flag staff of length 3 m. From a point on the field, the angles of elevation of the bottom and tip of the flag staff are 30° and 45° respectively. Which one of the following gives the best approximation to the height of the tower?

  4. Two poles are 10 m and 20 m high. The line joining their tops makes an angle of 15° with the horizontal. The distance between the poles is approximately equal to

  5. The angle of elevation of the top of a tower from a point 20 m away from its base is 45 °. What is the height of the tower?

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