JEE Main 2017 · MathsMultiple choiceSingle correctHardMulti-step

JEE Main 2 April 2017 (offline), Maths Q84

Question 84 of 90 in this shift, Maths question 24 of 30.

Let

\vec{a}=2\hat{i}+\hat{j}-2\hat{k}

and

\vec{b}=\hat{i}+\hat{j}

. Let

\vec{c}

be a vector such that

|\vec{c}-\vec{a}|=3

|(\vec{a}\times\vec{b})\times\vec{c}|=3

and the angle between

\vec{c}

and

\vec{a}\times\vec{b}

30^\circ

. Then

\vec{a}\cdot\vec{c}

is equal to :

(1)2Official answer
(2)5
(3) $\frac{1}{8}$
(4) $\frac{25}{8}$

Official answer

Option 1

CBSE answer key (25/04/2017, used for result).

Chapter: Vector Algebra
Topic: Cross Product
Idea tested: Magnitude and Sine Formula

Same idea in other shifts

Asked 6× in all

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Question text from the official JEE Main paper published by NTA (CBSE ran the 2017 exam); 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.