JEE Main 2022 · 27 Jun · Shift 1 · Mathematics Q15

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MathematicsSingle correct+4 / -1Question 15 of 90

Let $\vec a=\hat i+\hat j-\hat k$ and $\vec c=2\hat i-3\hat j+2\hat k$ . Then the number of vectors $\vec b$ such that $\vec b\times\vec c=\vec a$ and $\left|\vec b\right|\in\{1,2,\dots,10\}$ is :

Answer and worked solution

Official answer: A

Necessary condition. $\vec b\times\vec c$ is perpendicular to $\vec c$ , so we need $\vec a\cdot\vec c=0$ . But $\vec a\cdot\vec c=2-3-2=-3$ .

No such vector.

(A)

Topics:Cross product

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JEE Main 2022 · 27 Jun · Shift 1, Mathematics question 15