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Finding Rate of InterestCovid19 has led the world to go through a phenomenal transition . Elearning is the future today. Stay Home , Stay Safe and keep learning!!! For finding rate of interest P. a , we use the formula of amount only.A = ( 1 + r)^{n} Where, A = amount P = Principal r = rate in percent n = time in years. Examples on finding rate of interest: 1) At what rate percent P.a , compound interest will $ 10,000 amount to $ 13,310 in three years? Solution : Here, P = $ 10,000 ; A = $ 13,310 ; n = 3 years A = P ( 1 + r) ^{n} 13,310 = 10,000( 1 + r ) ^{3} 13,310/10,000 = ( 1 + r ) ^{3} 1331/1000 = ( 1 + r) ^{3} ( 11/10) ^{3} = ( 1 + r) ^{3} As the exponents are same the bases are equal. 11/10 = 1 + r 11/10 – 1 = r ( 11 – 10)/10 = r 1/10 = r As rate is in percent so, r = (1/10) x 100 Rate = 10 % P.a. 2) At what rate percent compound interest P.a. will $640 amount to $ 774.40 in 2 years ? Solution : Here, P = $ 640 ; A = $ 774.40 ; n = 2 years A = P ( 1 + r) ^{n} 774.40 = 640 ( 1 + r ) ^{2} 774.40 /640 = ( 1 + r ) ^{2} 77440 /64000 = ( 1 + r) ^{2} ( 88/80) ^{2} = ( 1 + r) ^{2} (11/10) ^{2} = ( 1 + r) ^{2} As the exponents are same the bases are equal. 11/10 = 1 + r 11/10 – 1 = r ( 11 – 10)/10 = r 1/10 = r As rate is in percent so, r = (1/10) x 100 Rate = 10 % P.a. Compound Interest ( CI ) • Find Compound Interest when interest is compounded Half yearly • Find Compound Interest when interest is compounded Quarterly • Find CI when interest is compounded annually but Rates are different • Finding Principal • Finding Time Period of Investment • Finding Rate of Interest Covid19 has affected physical interactions between people. Don't let it affect your learning.
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