Rs. 800 at 5% per annum compound interest will amount to

Let time be t years
∵ 882 = 800( 1 +5/1000)^t
⇒ 882/800 = (21/20)^t
⇒ (21/20)² = (21/20)^t
⇒ t =2
∴ Time = 2years