Q. The time in which 80000 Rs. Amounts to 92610 Rs. At 10% per annum compound interest, interest being compounded semi annually is :
Answer: 1.5 years
Notes: Time = t half year and R = 5% per half year $latex \therefore A = P\left ( 1+\frac{R}{100} \right )^{T}&s=1$ $latex => \frac{92610}{80000} = \left ( 1+\frac{5}{100} \right )^{T} = \left ( \frac{21}{20} \right )^{T}&s=1$ $latex => \frac{9261}{8000} = \left ( \frac{21}{20} \right )^{3}= \left ( \frac{21}{20} \right )^{T}&s=1$ ∴ T = 3 half years or $latex 1\frac{1}{2}&s=1$ years Hence option [A] is correct answer.

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