Time be t years
882 = 800 (1 +5/100) ^t 
=> 882/800 =(21/20) ^t 
 (21/20) ² = (21/20) ^t 
=> t = 2
Therefore, 
Time = 2 years

Amount = Rs. [7500 (1 +4/100)2] 
 = Rs. [7500 × 26/25 × 26/25] = Rs.8112

Principle = Rs.(8000/8) = Rs. 1000 
Therefore, C. I = Rs. [{ 1000 × (1 +4/100)² “ 1000}] 
= Rs. 81.60

Sum be Rs.100

S.I =
Rs.(1000/100) =Rs.10

X be the principle at the end of the first year

=> x =1320

Y be the original Principle

=> Y =1200

The principle is P. 
P(1 +10/100) ² “ P = 420 
=> P = Rs.2000 
S.I = Rs.(4000/100) = Rs.400

5000 × (1 +R/100) ² “ 5000 “(10000R/100)= 72 
=> 5000 [(1 + R/100) ² “ 1 “ R/50] = 72 
=> 1 + R²/100 + 2R/100 “ 1 “ R/50 = 72/5000 
=> R² = (72/5000 × 10000) = 144 or R =12%

P be the principle and R % Per annum be the rate. 
P(1 + R/100) ³ = 10648 - (i) 
P(1 + R/100) ² = 9680 - (ii) 
 By dividing (i) and (ii) 
(1 +R/100) = 10648/9680
Or 
R/100 = 968/9680 = 1/10 or 
R = 10 %

Sum be P 
P(1 + R/100) ³ = 6690 - (i) 
 P(1 + R/100) ² = 10, 035 - (ii) 
 By dividing (i) and (ii) 
(1 + R/100) ³ = 10035/6690 = 3/2 
Therefore, P = (6690 x 2/3) = Rs. 4460

P be the principle and R % per annum be rate 
P(1 + R/100) ³ = 3149.28 - (i) 
P(1 + R/100) ² = 2916 - (ii) 
 By dividing (i) and (ii) 
(1 + R/100) = 3149.28/2916 R/100 = 233.28/2916 
or R =233.28/2916 x 100 = 8 % 
P(1 +8/100) ² = 2916 or 
P × 27/25 × 27/25 = 2916 
Or = 1822500/729= Rs.2500