Question 703897:  The differance between simple interset and compound interest of a sum oof money $48 at 20% p.a for 2 years . Find the principal.. 
(Hint assume principal as100) 
 Answer by KMST(5328)      (Show Source): 
You can  put this solution on YOUR website! Following the hint, 
if you calculate the interest earned on $100 both ways: 
simple 20% p.a. interest for 2 years, 
and 20% p.a. compounded annually for 2 years, 
you find that compounded interest gives you $4 more. 
To get $48 extra from such compounding, you would need to invest 12 times more, or $1200.
 
To calculate on year's worth of interest at 20% p.a., we multiply the principal 
(the beginning balance) times  . 
$  at 20% interest for 1 year would earn $ . 
  
At 20% simple interest for 2 years, the second year interest would be calculated as another $ , based on the starting $ . 
The total interest for the 2-year period would be $ +$ =$ . 
  
If the interest was compounded annually, 
the balance at the end of the first year, 
$ +$ =$ , 
would be the new principal, used to calculate the interest on the second year.The interest for the second year would be 
$ =$ . 
That is an extra $  over what simple interest would yield. 
The $  for the second year comes from calculating interest on the interest 
already earned the first year. 
The $  is second year interest on the first year interest. 
That's called compounding the interest. 
  
NOTE: 
Interest can also be compounded monthly, daily, or continuously. 
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