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SSC Sample Paper Mock Test-12 SSC CGL Tear-II Paper-1

  • question_answer
    A certain amount gets double itself in 4 yr at the rate of certain percentage of compound interest annually. How much time it will take the amount to get 8 times of itself at the same rate of interest?

    A) 7 yr      

    B)  2 yr

    C)  15 yr   

    D)  None of these

    Correct Answer: B

    Solution :

    Suppose interest rate = r% per annum and principal amount = Rs. x Then, by question, \[x{{\left( x+\frac{r}{100} \right)}^{4}}=2\] After cubing both sides, we have \[{{\left[ x\left( x+\frac{r}{100} \right) \right]}^{12}}={{2}^{3}}\] So,       \[{{\left[ x\left( x+\frac{r}{100} \right) \right]}^{12}}=8\]times Therefore, the required time = 12 yr


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