1.

1). 12 years2). 13 years3). 9 years4). 16 years

Answer»

⇒ Let, Principal be Rs. x then Amount = Rs. 2x, RATE = r% and Time (n) = 3 years.

⇒ A = P× [1 + (r/100)]n

⇒ 2x = x × [1 + (r/100)] 3

⇒ 2 = [1 + (r/100)] 3 ------ 1

⇒ If SUM become 8 times in the time n years then,

⇒ 8 = [1 + (r/100)] n

⇒ 23 = [1 + (r/100)] n

⇒ putting the value of EQUATION 1 into above we GET,

⇒ ([1 + (r/100)] 3)3 = [1 + (r/100)] n

∴ n = 9



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