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Three quantities X, Y and Z are such that XY=kZ where k is constant. Initially, X was at 4 and X:Y:Z was 2:3:4. If the value of Y is changed to 12 and Z is kept constant, find the value of X.

Correct answer: A. 2

  • A. 2
  • B. 3
  • C. 5
  • D. 6

Explanation

Initially, X:Y:Z = 2:3:4 and X = 4, so one ratio unit is 2 and the initial values are Y = 6 and Z = 8. Since XY = kZ and Z remains constant, XY remains constant: 4 × 6 = X × 12, so X = 24 ÷ 12 = 2. The likely trap is option b, 3, from treating X and Y as directly proportional rather than recognizing that their product is constant when Z is fixed.

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