Q. In how may years will Rs. 2000 amounts to Rs. 2420 at 10% per annum compound interest?
Answer: 2 years
Notes: According to question, $latex 2420=2000\left ( 1+\frac{10}{100} \right )^{t}&s=1$ $latex =>\frac{2420}{2000}=\left ( \frac{11}{10} \right )^{t}&s=1$ $latex =>\frac{121}{100}=\left ( \frac{11}{10} \right )^{t}&s=1$ $latex =>\left ( \frac{11}{10} \right )^{2}=\left ( \frac{11}{10} \right )^{t}&s=1$ ∴ t = 2 years Hence option [C] is the right answer.

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