Compound Interest MCQ Question with Answer

Principal = Rs. 1000; Amount = Rs. 1331; Rate = 10% p.a. Let the time be n years.
Then, [ 1000 (1+ (10/100))ⁿ ] = 1331 or (11/10)^{n =} (1331/1000) = (11/10)³

n = 3 years.

          Principal = Rs. 500; Amount = Rs. 583.20; Time = 2 years.                                                                            
           Let the rate be R% per annum..
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           Then,      [ 500 (1+(R/100)² ] = 583.20 or [ 1+ (R/100)]^{2 =} 5832/5000 = 11664/10000

                            [ 1+ (R/100)]² = (108/100)² or 1 + (R/100) = 108/100 or R = 8

Clearly, Rate = 5% p.a., Time = 3 years, S.I.= Rs. 1200.    

So principal=RS [100*1200]/3*5=RS 8000

Amount = Rs. 8000 x [1 +5/100]^3 - = Rs. 9261.

 C.I. = Rs. (9261 - 8000) = Rs. 1261.

Principal = Rs. 10000; Rate = 2% per half-year; Time = 2 years = 4 half-years.         

       Amount =Rs [10000 * (1+(2/100))⁴] = Rs(10000 * (51/50) * (51/50) * (51/50) * (51/50))          

                   = Rs. 10824.32.

       :. C.I. = Rs. (10824.32 - 10000) = Rs. 824.32.

               Principal = Rs. 16000; Time = 9 months =3 quarters;

                Rate = 20% per annum = 5% per quarter.

                Amount = Rs. [16000 x (1+(5/100))³] = Rs. 18522.

                            = Rs. (18522 - 16000) = Rs. 2522.

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

      therefore, C.I. = Rs. (8112 - 7500) = Rs. 612.

            Time = 2 years 4 months = 2(4/12) years = 2(1/3) years.                                                                                     Amount = Rs'. [8000 X (1+­(15/100))² X (1+((1/3)*15)/100)]

                                 =Rs. [8000 * (23/20) * (23/20) * (21/20)]

                                 = Rs. 11109.                            .

                      :. C.I. = Rs. (11109 - 8000) = Rs. 3109.