Subject: General Aptitude · Chapter: Heights and Distances · Exam: · Marks: · Difficulty:
The angle of elevation of the top of a tower at a point on the ground is 30°. On walking 24 m towards the tower, the angle of elevation becomes 60°. Find the height of the tower.
Answer
Answer (as printed):
Explanation
Let AB be the tower and C and D be the points of observation. Then, AB AB h B = tan 60° = 3 ⇒ AD = = . AD 3 3 AB 1 = tan 30° = ⇒ AC = AB × 3 = h 3. h AC 3 h 30° 60° CD = (AC − AD) = h 3 − . 3 C 24 m D A h ∴ h 3− = 24 ⇒ h = 12 3 = (12 × 1.73) = 20.76. 3 Hence, the height of the tower is 20.76 m.
Explanation as extracted from the printed page; notation may be imperfect.