Puzzle 6: What’s the radius of the circle?

A simple geometry problem. Shouldn’t take more than a minute to come up with the answer.

The following diagram (not to scale) shows a circle with the center at point C. What is the radius of the circle?


Give proper explanation with your answer.

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5 comments so far

  1. ujj on

    The right angles make the inner figure a rectangle, whose diagonals are of equal length.

  2. CoolDude on

    it shud be 11 i guess…as tan45=(r-3)/8, so r=11.Am I right.

  3. Vivek Mungala on


  4. iRattle on


    8= sqrt[ (r/2)^2 + (r-3)^2]

    solving for r gives 7.156 🙂

  5. sreedharmuthalagiri on

    ujj is absolutly correct. one of the diagonals of the rectangle is the radius of the circle. since diagonals of a rectangle is equal, the radius of the circle is 8.

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