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NDA 2018 Maths · Mathematics · Matrices · easy

For what value of k does the system x+2y=3, 2x+ky=6 have infinitely many solutions?

Single correct option

For what value of kk does the system x+2y=3x+2y=3, 2x+ky=62x+ky=6 have infinitely many solutions?
  1. A. 4
  2. B. 2
  3. C. 3
  4. D. 6
Show answer and solution

Answer: (A) 4

The second equation must be a multiple of the first: multiplying x+2y=3x+2y=3 by 2 gives 2x+4y=62x+4y=6, so k=4k=4. For any other kk the lines meet in one point; there is never a 'no solution' case here since the right sides are already proportional.
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Original question written in the NDA 2018 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake