JEE Main 2019MathematicsVector AlgebraEasyMCQ

JEE Main 2019 — Vector Algebra Question with Solution

JEE Main 2019 (09 Jan Shift 1)

Question

Let a→=i^-j^,  b→=i^+j^+k^ and c→ be a vector such that a→×c→+b→=0→ and a→.c→=4, then |c→|2 is equal to:

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Show full solutionCorrect option: A
Correct answer
A192

Step-by-step explanation

Let the angle between a→ and c→ is θ.

∴  cos⁡θ=a→ . c→a→ c→=42 c→

Given, a→×c→+b→=0

⇒  a→×c→=b→

⇒  a→. c→sin⁡θ=b→

⇒   a→2c→2sin2⁡θ=b→2

⇒  2c→21-cos2⁡θ=3

⇒  2c→21-162c→2=3

⇒  2c→2-16=3

⇒   c→2=192

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About this question

This is a previous-year question from JEE Main 2019, covering the Vector Algebra chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.