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Home Aptitude Height and Distance See What Others Are Saying!
  • Question
  • A person standing on the bank of a river observes that the angle subtended by a tree on the opposite bank is 60°, when he retires 40 meters from the bank then he find the angle to be 30°. Then the breadth of the river is?


  • Options
  • A. 40 m
  • B. 60 m
  • C. 20 m
  • D. 30 m

  • Correct Answer
  • 20 m 

    Explanation

    Let us draw a figure below as per given question.
    Let A be the position of a person on the bank of a river and OP the tree on the opposite bank and ?OAP = 60°. When the person retires to the position B, then AB = 40 meter and ?OBP = 30°
    Let us assume OA(Breadth of the river) = x meter and height of tree OP = h meter
    In ?OAP, Use the trigonometry formula
    Tan60° = P/B = Perpendicular distance / Base distance
    ? Tan60° = OP / OA
    ? OP = OA Tan60°
    Put the value of OP and OA, We will get
    ? h = x?3 ..............(1)
    Now in the triangle ?OBP
    Tan30° = OP / OB
    ? OP = OB Tan30°
    ? OP = (x + 40)/?3
    ? h = (x + 40)/?3 ...................(2)
    From Equation (1) and (2), We will get
    ? (x + 40)/?3 = x?3
    ? (x + 40) = x?3 X ?3
    ? (x + 40) = 3x
    ? 3x - x = 40
    ? x = 20 m


  • More questions

    • 1. 
      A and B together can complete a work in 3 days. They started together but after 2 days, B left the work. If the work is completed after 2 more days, B alone could do the work in how many days?

    • Options
    • A. 5
    • B. 6
    • C. 7
    • D. 10
    • Discuss
    • 2. 
      A wheel makes 1000 revolutions in covering a distance of 88 km. the diameter of the wheel is?

    • Options
    • A. 24 meters
    • B. 40 meters
    • C. 28 meters
    • D. 14 meters
    • Discuss
    • 3. 25, 36, 49, 81, 121, 169, 225

    • Options
    • A. 36
    • B. 49
    • C. 121
    • D. 169
    • Discuss
    • 4. 
      (.896 x .752 +.896 x .248) / (.7 x .034 + .7 x.966) =?

    • Options
    • A. 1.28
    • B. 0.976
    • C. 12.8
    • D. 9.76
    • Discuss
    • 5. 
      Einstein goes from Ahmedabad To Lucknow at the speed of 40 km/hr and returned at the speed of 60 km/hr .the average speed of Einstein during the whole journey is

    • Options
    • A. 48 km/hr
    • B. 24 km/hr
    • C. 50 km/hr
    • D. none of these
    • Discuss
    • 6. 
      Today is Monday. After 61 days, it will be

    • Options
    • A. Wednesday
    • B. Saturday
    • C. Tuesday
    • D. Thursday
    • Discuss
    • 7. 9548 + 7314 = 8362 + (?)

    • Options
    • A. 8230
    • B. 8410
    • C. 8500
    • D. 8600
    • E. None of these
    • Discuss
    • 8. 
      The true discount on a certain sum due 1 yr hence at 30% per annum, is ? 240. What is the banker' discount on the same sum for the same time and at the same rate?

    • Options
    • A. ? 400
    • B. ? 212
    • C. ? 312
    • D. ? 445
    • Discuss
    • 9. 
      Calendar of month July is same as that of which month of previous year.

    • Options
    • A. May
    • B. September
    • C. April
    • D. None of these
    • Discuss
    • 10. 
      A coin is successively tossed two times. Find the probability of getting? (1) exactly one head (2)at least one head

    • Options
    • A. 1/2 , 3/4
    • B. 2/3, 1/4
    • C. 1/4, 4/5
    • D. 1/2, 2/3
    • Discuss


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