All Exams  >   RRB NTPC/ASM/CA/TA  >   Mathematics for RRB NTPC / ASM  >   All Questions

All questions of Height & Distance for RRB NTPC/ASM/CA/TA Exam

A man standing on the terrace of a building watches a car speeding towards him. If at that particular instant the car is 200 m away from the building makes an angle of depression of 60° with the man’s eye and after 8 seconds the angle of depression is 30°, what is the speed of the car?
  • a)
    15 m/s
  • b)
    25 m/s
  • c)
    16.67 m/s
  • d)
    Cannot be determined
Correct answer is option 'C'. Can you explain this answer?

Understanding the Problem
The problem involves a man on a terrace observing a car. We need to determine the speed of the car based on angles of depression at two different times.
Given Data
- Initial distance from the car to the building: 200 m
- Initial angle of depression: 60°
- Angle of depression after 8 seconds: 30°
Calculating Heights and Distances
1. Initial Height Calculation:
- Using the angle of depression (60°):
- The height (h) of the terrace can be calculated using the tangent function:
- h = 200 * tan(60°) = 200 * √3
2. Position After 8 Seconds:
- After 8 seconds, the car makes an angle of depression of 30°:
- The new horizontal distance (d) from the building can be calculated:
- h = d * tan(30°)
- d = h / tan(30°) = (200 * √3) / (1/√3) = 600 m
Calculating the Distance Traveled by the Car
- Total Distance Covered:
- Initially, the car was 200 m away and is now 600 m away.
- Distance traveled = 600 m - 200 m = 400 m
Calculating Speed of the Car
- Speed Calculation:
- Speed = Distance / Time
- Speed = 400 m / 8 s = 50 m/s
Conclusion
The calculated speed of the car is incorrect in terms of the options provided. Therefore, if the answer is indeed stated as 16.67 m/s, it suggests a different interpretation or calculation might be needed. The correct approach leads to a clear understanding of the problem's requirements and the progression of the car's movement based on the angles of depression observed.

A ship is approaching an observation tower. If the time taken by the ship to change the angle of elevation from 30° to 45° is 10 minutes, then find the time the ship will take to cover the remaining distance and reach the observation tower assuming the ship to be travelling at a uniform speed.
  • a)
    15 minutes 20 seconds
  • b)
    13 minutes 40 seconds
  • c)
    16 minutes 40 seconds
  • d)
    Cannot be determined
Correct answer is option 'B'. Can you explain this answer?


Let AB be the observation tower and h be its height.
Also, let the ship be at C when the angle of elevation is 30° and at D when the angle of elevation is 45°.
The time taken by the ship to travel from C to D is 10 minutes and we need to find out the time the ship will take to reach B from D.
∴ tan 30º = AB/CB = h / CB = 1/ √3
⇒ CB = √3 x h
∴ tan 45º = AB / DB = h / DB = 1
⇒ DB = h
⇒ CD = CB – DB = (√3h – h) = h(√3– 1)
Now, as h(√3 – 1) distance is covered in 10 minutes, a distance of h is covered in = 13.66 minutes = 13 minutes 40 seconds

An aeroplane when 750 m high passes vertically above another aeroplane at an instant when their angles of elevation at same observing point are 45° and 30&de; respectively. Approximately, how many meters higher is the one than the other?
  • a)
    250(1- √3)
  • b)
    750(3- √3)
  • c)
    250(3- √3)
  • d)
    275(1- √3)
Correct answer is option 'C'. Can you explain this answer?

Ssc Cgl answered

Let C and D be the position of the aeroplanes.
Given that CB = 900 m,∠CAB = 60°,∠DAB = 45°
From the right △ ABC,
Tan45 = CB/AB => CB = AB
From the right △ ADB,
Tan30 = DB/AB => DB = ABtan30 = CBx(1/√3) = 750/√3
CB = CD + DB
=> Required height CD = CB - DB = 750 - 750/√3 = 250(3 - √3)

Two men are inverse sides of a tower. They gauge the edge of the rise of the highest point of the tower as 30° and 45° respectively. On the off chance that the tallness of the tower is 50 m, discover the separation between the two men. (Take √3=1.732)
  • a)
    135.5m
  • b)
    136.5 m
  • c)
    137.5 m
  • d)
    138.5m
Correct answer is option 'B'. Can you explain this answer?

EduRev SSC CGL answered

Let AB be the tower and let C and D be the two's positions men.
At that point ∠ACB = 30°,∠ADB = 45°and AB = 50 m
AC/AB = Cot30° = √3 => AC/50 = √3
=> AC = 50√3m
AD/AB = cot 45° = 1 => AD/50 = 1
=> AD = 50M.
Separation between the two men = CD = (AC + AD)
= (50√3 + 50) m = 50(√3 + 1)
=50(1.73 + 1)m = (50 * 2.73)m = 136.5m.

Chapter doubts & questions for Height & Distance - Mathematics for RRB NTPC / ASM 2025 is part of RRB NTPC/ASM/CA/TA exam preparation. The chapters have been prepared according to the RRB NTPC/ASM/CA/TA exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for RRB NTPC/ASM/CA/TA 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

Chapter doubts & questions of Height & Distance - Mathematics for RRB NTPC / ASM in English & Hindi are available as part of RRB NTPC/ASM/CA/TA exam. Download more important topics, notes, lectures and mock test series for RRB NTPC/ASM/CA/TA Exam by signing up for free.

Signup to see your scores go up within 7 days!

Study with 1000+ FREE Docs, Videos & Tests
10M+ students study on EduRev