In what time will ₹ 1000 amounts to ₹ 1331 at 20% per

In what time will ₹ 1000 amounts to ₹ 1331 at 20% per annum, compounded half yearly ?

Given that , P = ₹ 1000 , A = ₹ 1331
Let the required time be t years.
Interest is compounded half yearly
∴ Time = 2t half years

and rate =	20	= 10%
	2

∴ 1000		1 +	10		^2t	= 1331
			100

⇒		11			^2t	=	1331
		10					1000

⇒		11		^2t	=		11		³	⇒2t = 3
		10					10

∴ t =	3	years or 1	1	years
	2		2