technology and zen of life

“A heisenbug (named after the Heisenberg Uncertainty Principle) is a computer bug that disappears or alters its characteristics when an attempt is made to study it.”

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.

After all we all know the radius of the circle is pi*r^2. right ?

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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6 Responses

  1. sreedharmuthalagiri says:

    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.

  2. iRattle says:


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

    solving for r gives 7.156 🙂

  3. Vivek Mungala says:


  4. CoolDude says:

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

  5. ujj says:

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


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