[Trigonometry] HnD Type #5: Finding speed, time or distance made easy for SSC

Aptitude10 Comments

  1. Introduction: Trigonometry Speed Time Distance
  2. Approach:Trigonometry Speed Time Distance
  3. Mock questions

Introduction

Continuing in the series of “Trigonometry –>Height and Distance(HnD)–> Five types of Questions.

5th and the last type of question is “finding speed, time or distance”. Here are example questions (both solved in the video)

  1. A jet is flying at a constant height of 4500 root 3meters. Angle of elevation of the jet from a point on ground is 60 Degrees. After 30 seconds of flight, this angle becomes 30 degrees. Find speed of this jet plane.
  2. A car is 60m away from a building. Angle of elevation is 45. After 5 seconds, car moves away from the building and angle is decreased to 30. Find speed of this car.

Approach

  • Basically approach is same as “one building two angles” type of questions.= Since two angles are given, you make two equations of “TAN” using Topi-triangle shortcutTM and you get a distance.
  • Then apply “STD” formula (speed x time = distance) and you’ll get the answer.
  • Check the following video to see it in detail and after watching the video, solve the mock questions given at the bottom of this article.


If the video is not visible, check it directly on youtube by clicking me

Mock questions

Ht n Dist Type5

  1. A 1.3 m tall man spots a balloon moving with the wind in a horizontal line at a constant height of 91.3 m above the ground. The angle of elevation of this balloon is 60°. After some time the angle is reduced to 30°. Find the distance travelled by the balloon during this interval
  2. From a 100m tall lighthouse, the angle of depression of a ship is 30. After some time, angle of depression increases to 45. Find the distance travelled by ship during this time interval. (hint: STD formula unnecessary here!)
  3. A man on the top of building observes a car moving at a uniform speed and coming directly towards the building.  it takes 12 minutes for the angle of depression to change from 30 to 45, how soon after this, will the car reach the building?

Answers

  1. 60 root 3 OR 103.8m
  2. 73m
  3. 16.38 minutes

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So far 10 Comments posted

  1. Natasha

    thanks a lot sir………………

  2. Abhi

    Its really very conceptual.thanks a lot

  3. TARUN

    Thamks a lot sir… All articles r verry useful…
    In this article, i hv some difficulty in mock questions 1 and 3.. so plz help me for sollution…
    Thanks..

  4. vandy

    a man cover 2/5 of journey in 1 hr, and 1/5 of journey in 1 hr and 45 min to cover remaining 220km. find total dist.

  5. zain

    It is so awesome and useful
    Because i need some airplanes knowledge so
    ThAnKs

  6. kavita

    plz kuch videos quantitude aptitude p free of cost provide kr dijiye

  7. Manu Reddy

    Sir, could you explain 3rd question.

  8. deepak

    left out time for the exam is 6 days in hand,can i have a fast track revision from topic 1 to last topic…

  9. Aspirant

    can any1 please show the steps for 3rd problem in the mock test?

  10. Sourin Gorai

    Please tell me the age limit of OBC candidate?

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