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Saturday, 31 October

JEE Main 2021 · MathsMultiple choiceSingle correctMediumApplication

JEE Main 25 February 2021, Shift 1, Maths Q79

Question 79 of 90 in this shift, Maths question 19 of 30, Section A.

A man is observing, from the top of a tower, a boat speeding towards the tower from a certain point A, with uniform speed. At that point, angle of depression of the boat with the man's eye is 30∘30^\circ (Ignore man's height). After sailing for 20 seconds, towards the base of the tower (which is at the level of water), the boat has reached a point B, where the angle of depression is 45∘45^\circ. Then the time taken (in seconds) by the boat from B to reach the base of the tower is :
  1. (1)10
  2. (2)10(3+1)10(\sqrt{3} + 1)Official answer
  3. (3)10310\sqrt{3}
  4. (4)10(3−1)10(\sqrt{3} - 1)

Official answer

Option 2

NTA final key.

Chapter
Trigonometric Functions
Topic
No close match in our taxonomy
Idea tested
No close match in our taxonomy

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.