The compound interest on a sum of money for 2 years is rs 615 and the simple interest for the same period is rs 600. What is the principal?

• SI will be same for each year.
  Hence,
  SI of 1st year=600/2=300
  On the 2nd year he gave CI as: 300+
  (300*R%)
  CI-SI=615-600=15
  300*R%=15
  R=5%
  P*R%=300
  P=300/5%=300*100/5=6000
• 7 years agoHelpfull: Yes(10) No(3)
• S.I. = PRT/100 => 600=2PR =>PR=30000..............(1)
  C.I. = P(1+R/100)^n-P =>615=P[(1+ R/100)^2--1]..............after solving we get result as
  6150000=30000R + 6000000 =>R=5
  Now put in equation (1)
  we get PR=30000 =>P=30000/5 =>P=6000 Ans
• 7 years agoHelpfull: Yes(1) No(0)
• difference b/w C.I & S.I. for 2 yrs on sum Rs.P at R%, d=P(R/100)^2 ,and also d=(S.I. x R)/200 for 2 yrs at R% , where 'd' is difference,
  so, here difference d=615-600=15,
  using in d=(S.I. x R)/200 , i.e. R=(d x 200)/S.I.
  So. R=(15 x 200) / 600 ,i.e. R=5 %
  
  but also ,d=P(R/100)^2 , So P=d(100/R)^2
  
  ==> P = 15(100/5)^2, .'. P = 400 x 15 = 6000 , Principal value ,P=Rs.6000
• 7 years agoHelpfull: Yes(0) No(0)
• CI=R+R+R*R/100........EQ1
  SI=R+R..........EQ2
  EQ1-EQ2
  SO,R*R/100=15
  R*R=1500
  R=10√15
  SO,SI=P*R*T/100
  FOR 1 YEAR
  300=P*10√15 *1/100
  P=3000/√15
• 7 years agoHelpfull: Yes(0) No(0)