A sum of Rs. 2000 amounts to Rs. 4000 in two years at compound

A sum of Rs. 2000 amounts to Rs. 4000 in two years at compound interest. In how many years will the same amount become Rs. 8000 ?

Here , Amount ( A ) = Rs. 4000 , P = Rs. 2000 , Rate = R% , Time = 2 years
Using the given formula ,

A = P		1 +	R		^T
			100

⇒ 4000 = 2000		1 +	R		²
			100

⇒ 2 =		1 +	R		²
			100

⇒ 1 +	R	= √2 ......(1)
	100

Again , Amount ( A ) = Rs. 8000 , P = Rs. 2000 , Rate = R% , Time = ?

∴ 8000 = 2000		1 +	R		^T
			100

⇒ 4 = (√2)^T { Using (1) }
⇒ (√2)⁴ = (√2)^T
⇒ T = 4 years