a sum of money lent out a simple interest doubled itself in 20 years. in how many years will it treble itself?
option
a)none
b)40
c)30
d)50

• b) 40
  If Sum=x,interest rate=r,t=20 then, x*20*r/100=x , r=5
  To triple the amount x*t*5/100=2x, t=40
• 11 years agoHelpfull: Yes(15) No(5)
• here sum is doubles in 20 years =>
  consider sum = x and si = 2x now put values in formula we get r = 10%
  now to triple the sum consider sum = x , si = 3x , r = 10% and again put values in the fromula(si = (sum*r*t)/100) we get t = 30 years
  please correct me if a am wrong
  answer=>b)30
• 11 years agoHelpfull: Yes(6) No(13)
• a/c, (p*r*20)/100 = 2p
  =>r = 10
  therfore,(p*10*t)/100 = 3p
  => t = 30 years
• 11 years agoHelpfull: Yes(3) No(2)
• c)30 interest=10%
• 11 years agoHelpfull: Yes(2) No(2)
• 40
  100(n-1)=rt
  100/20=t
  t=5
  therefore t=100*2/5
  =40(ans)
• 10 years agoHelpfull: Yes(2) No(1)
• (n - 1) x 100 = rt
  
  In the first part of given problem n = 2 & t = 20
  
  Plugging values, (2 - 1) x 100 = r x 20
  
  => r = 5%
  
  For the second part of problem, plug in newly obtained values of r and n = 3 :
  
  (3 - 1) x 100 = 5 x t
  
  t = 200/5= 40 years.
• 6 years agoHelpfull: Yes(0) No(0)