Q. 1000 Rs. is invested at 5% per annum simple interest. If the interest is added to the principal after every 10 years, the amount will become 2000 Rs. after :
Answer: $latex 16\frac{2}{3}\ years&s=1$
Notes: $latex \mathbf{16\frac{2}{3}}\ years&s=1$
After 10 years $latex SI = \frac{1000\times 5\times 10}{100} = 500\ Rs.&s=1$ Principal for 11th year = 1000 + 500 = 1500 Rs. $latex \therefore T = \frac{SI\times 100}{P\times R} = \frac{500\times 100}{1500\times 5}&s=1$ $latex = \frac{20}{3}\ years = 6\frac{2}{3}\ years&s=1$ ∴ Total time $latex = 10+6\frac{2}{3} = 16\frac{2}{3}\ years&s=1$ Hence option [B] is correct answer.

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