JEE Main 2017MathematicsVector AlgebraEasyMCQ

JEE Main 2017 — Vector Algebra Question with Solution

JEE Main 2017 (02 Apr)

Question

Given, a→=2i^+j^-2k^ and b→= i^+j^. Let c→ be a vector such that c→- a→=3, a→×b→×c→=3 and the angle between c→ and a→×b→ be 30° . Then a→⋅c→ is equal to:

Choose an option

Show full solutionCorrect option: B
Correct answer
B2

Step-by-step explanation

Given,

a→=2i^+j^-2k^

b→=i^+j^

Now,

a→×b→=i^j^k^21-2110

⇒a→×b→=2i^-2j^+k^

⇒a→×b→=3

Given,

a→×b→×c→=3

⇒a→×b→c→sin30°=3

⇒c→=2

Now,

c→-a→=3

⇒c→-a→2=9

⇒c→2+a→2-2a→·c→=9

⇒a→.c→=2

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About this question

This is a previous-year question from JEE Main 2017, 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.