A certain sum of money becomes 3 times of itself in 10 years at simple interest. In how many years does it become double of itself at the same rate of simple interest?

Let the principal = Rs. x, Amount = Rs. 3x, Time = 10 years ∴ Simple Interest = Rs. (3x – x) = Rs. 2x Rate = [(2x × 100)/(x × 10)]% p.a. = 20% p.a. Now, Principal = Rs. x, Amount = Rs.2x, Rate = 20%p.a. Simple Interest= Rs. (2x − x)= Rs. x ∴ Time =(x × 100)/(x × 20) = 5 years.

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