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AP EAMCET20225 Jul 2022Morning ShiftMathematicsVector AlgebraActual

If a is collinear with b =3 i +6 j +6 k and a b =27 , then | a |=

Options

  1. A1
  2. B2
  3. C3
  4. D4

Correct answer

C. 3

Step-by-step solution

Let a =x i +y j +z k , b =3 i +6 j +6 k a b =27 According to question, a is a collinear with b , then a = b ...(i) a b =27 b b =27 [from Eq. (i)] | b |^2=27 = 27 ( (3)^2+(6)^2+(6)^2 )^2 = 27 (9)^2 = 1 3 a = 1 3 (3 i +6 j +6 k ) a = i +2 j +2 k So, | a |= 1+(2)^2+(2)^2 = 9 =3 units

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