A sum of money doubles in 12 years. In how many years, it will treble at S.I.	Choose the most appropriate option.
A) 12 years	B) 8 years	C) 6 years	D) 24 years	E) 36 years
Explanation :   Simple Interest, SI = PRT/100   i.e, SI ∝ T when rate(R) and principal (P) are constants   Let x be the sum of money and which will treble in n years   (Please note that when the money doubles, simple interest is 2x - x = x   and when the money trebles, simple interest is 3x - x = 2x)   (2x-x) ∝ 12   =&gt; x ∝ 12 -------------(1)   (3x-x) ∝ n   =&gt; 2x ∝ n -------------(2)   From (1) and (2),   x/2x=12/n 1/2=12/n⇒n = 24 years   i.e, in 24 years, the money will treble   Answer : Option 24 years
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A sum of money doubles in 12 years. In how many years, it will treble at S.I.