JEE Main & Advanced Mathematics Sequence & Series Question Bank Geometric Progression

  • question_answer
    0.14189189189?. can be expressed as a rational number [AMU 2000]

    A) \[\frac{7}{3700}\]

    B) \[\frac{7}{50}\]

    C) \[\frac{525}{111}\]

    D) \[\frac{21}{148}\]

    Correct Answer: D

    Solution :

    0.14189189189.... \[=0.14+0.00189+0.00000189+.......\] \[=\frac{14}{100}+189\left[ \frac{1}{{{10}^{5}}}+\frac{1}{{{10}^{8}}}+....\infty  \right]\] \[=\frac{7}{50}+189\,\left[ \frac{1/{{10}^{5}}}{1-(1/{{10}^{3}})} \right]\]\[=\frac{7}{50}+189\,\left[ \frac{1}{{{10}^{5}}}\times \frac{{{10}^{3}}}{999} \right]\] \[=\frac{7}{50}+\frac{189}{999\times 100}\] \[=\frac{7}{50}+\frac{7}{3700}=\frac{7}{50}+\frac{7}{25\times 148}\]\[=\frac{21}{148}\].


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