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Railways R.R.C. (Patna) Solved Paper Held on 1st Shift 2-11-2014

  • question_answer
    The area of a circle is increased by \[22\,\,c{{m}^{2}}\] when it' radius is increased by 1 cm. The original radius of the circle is?

    A) 6 cm                            

    B) 3-2 cm

    C) 3 cm                            

    D) 3-5 cm

    Correct Answer: C

    Solution :

    Suppose the original radius of the circle =r cm Then,    \[\pi {{r}^{2}}+22=\pi {{(r+1)}^{2}}\] \[\pi {{r}^{2}}+22=\pi ({{r}^{2}}+1+2r)\] \[22=(1+2r)\frac{22}{7}\] \[7=1+2r\] \[2r=6\] \[r=3\,\,cm\]


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