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Friday, 9 October

JEE Main 2025 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 2 April 2025, Shift 1, Maths Q11

Question 11 of 75 in this shift, Maths question 11 of 25, Section A.

If a⃗\vec{a} is a nonzero vector such that its projections on the vectors 2i^−j^+2k^2\hat{i}-\hat{j}+2\hat{k}, i^+2j^−2k^\hat{i}+2\hat{j}-2\hat{k} and k^\hat{k} are equal, then a unit vector along a⃗\vec{a} is :
  1. (1)1155(−7i^+9j^−5k^)\frac{1}{\sqrt{155}}\left(-7\hat{i}+9\hat{j}-5\hat{k}\right)
  2. (2)1155(−7i^+9j^+5k^)\frac{1}{\sqrt{155}}\left(-7\hat{i}+9\hat{j}+5\hat{k}\right)
  3. (3)1155(7i^+9j^−5k^)\frac{1}{\sqrt{155}}\left(7\hat{i}+9\hat{j}-5\hat{k}\right)
  4. (4)1155(7i^+9j^+5k^)\frac{1}{\sqrt{155}}\left(7\hat{i}+9\hat{j}+5\hat{k}\right)Official answer

Official answer

Option 4

NTA final key.

Same idea in other shifts

Asked 2× in all
  1. 29 Jun 2022, Shift 1 · Q5Let a⃗=αi^+3j^−k^\vec{a} = \alpha\hat{i} + 3\hat{j} - \hat{k}, b⃗=3i^−βj^+4k^\vec{b} = 3\hat{i} - \beta\hat{j} + 4\hat{k} and…MediumSingle correct

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 42 of the 174 JEE Main shifts held from 2017 to 2026.