JEE Main 2020 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 8 January 2020, Shift 2, Maths Q67

Question 67 of 75 in this shift, Maths question 17 of 25, Section A.

Let

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

and

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

be two vectors. If

\vec{c}

is a vector such that

\vec{b} \times \vec{c} = \vec{b} \times \vec{a}

and

\vec{c} \cdot \vec{a} = 0

, then

\vec{c} \cdot \vec{b}

is equal to :

(1) $\frac{1}{2}$
(2) $-\frac{1}{2}$ Official answer
(3) $-1$
(4) $-\frac{3}{2}$

Official answer

Option 2

NTA final key (Jan 2020).

Chapter: Vector Algebra
Topic: Cross Product
Idea tested: Solving Vector Equations with Cross Products

Same idea in other shifts

Asked 20× in all

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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.