JEE Main · 2021 · 16 Mar 2021 · Shift 2 · Vector Algebra

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Let and .
If and , then the value of is equal to :
  1. (A)9
  2. (B)11
  3. (C)15✓ Correct
  4. (D)13

Answer: (C)

Solution

Since , the first condition is , so is parallel to and .
The two scalar products give

that is and . The second becomes , so and then . Hence with , so .

JEE Main · 2021 · 16 Mar 2021 · Shift 2 · Single correct option

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