A company publishes to its customers that at a certain compound interest rate, a sum of money deposited by anyone will become 8 times in 3 years. If the same amount is deposited at the same compound rate of interest, then in how many years will it become 16 times ?
If a sum of money becomes $$x$$ times in $$a$$ years, it will become $$y$$ times in $$b$$ years
=> $$(x)^{\frac{1}{a}}=(y)^{\frac{1}{b}}$$
Similarly, $$(8)^{\frac{1}{3}}=(16)^{\frac{1}{t}}$$
=> $$(2)^{\frac{3}{3}}=(2)^{\frac{4}{t}}$$
=> $$1=\frac{4}{t}$$
=> $$t=4$$ years
=> Ans - (A)
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