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MHT CET202019 Oct 2020Morning ShiftMathematicsVector AlgebraActual

If a , b , c are nonzero vectors along the coterminus edges of a parallelopiped with volume 7 cubic units, then the volume of a parallelopiped with a + b , b + c , c + a as the coterminus edges is

Options

  1. A49 cubic units
  2. B2 cubic units
  3. C14 cubic units
  4. D7 cubic units

Correct answer

C. 14 cubic units

Step-by-step solution

(A) We have [ a ( b c )]=7[ a + b b + c c + a ]=( a + b ) [( b + c ) ( c + a )]=( a + b ) [( b c )+( b a )+( c c )+( c a )]=[ a ( b c )]+[ a ( b a )]+[ a ( c a )]+[ b ( b c )]+[ b ( b a )]+[ b ( c a )]=[ a ( b c )]+0+[ b ( c a )]=[ a ( b c )]+[ a ( b c )]=2[ a ( b c )]=2(7)=14

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