Circles · Class 9 · CBSE Mathematics

If a line intersects two concentric circles with center O at points A, B, C, and D in that order, which of the following is always true regarding the…

Practice question from Circles (Class 9 · CBSE Mathematics), with the correct answer and a step-by-step solution.

medium · MCQ · Q-7741EF

If a line intersects two concentric circles with center O at points A, B, C, and D in that order, which of the following is always true regarding the lengths of line segments?

  1. A.AB = CDCorrect answer
  2. B.AC = BD
  3. C.AD = BC
  4. D.AB > CD

Solution

Draw a perpendicular from the center OO to the line. Let it meet the line at MM. Since the perpendicular from the center to a chord bisects the chord, we have AM=MDAM = MD (for the outer circle) and BM=MCBM = MC (for the inner circle). Subtracting the two gives AM−BM=MD−MCAM - BM = MD - MC, which means AB=CDAB = CD.

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