At 6.10 percent interest, how long does it take to double your money? (Round your answer to 2 decimal places. (e.g., 32.16))
Length of time  years 
At 6.10 percent interest, how long does it take to quadruple it? (Round your answer to 2 decimal places. (e.g., 32.16))

Length of time  years 
Explanation:
To
find the length of time for money to double, triple, etc., the present
value and future value are irrelevant as long as the future value is
twice the present value for doubling, three times as large for tripling,
etc. We can use either the FV or the PV formula. Both will give the
same answer since they are the inverse of each other. We will use the FV
formula, that is:

FV = PV(1 + r)^{t} 
Solving for t, we get: 
t = ln(FV / PV) / ln(1 + r) 
The length of time to double your money is: 
FV = $2 = $1(1.061)^{t} 
t = ln(2) / ln(1.061) = 11.71 years 
The length of time to quadruple your money is: 
FV = $4 = $1(1.061)^{t} 
t = ln(4) / ln(1.061) = 23.41 years 
Notice
that the length of time to quadruple your money is twice as long as the
time needed to double your money (the difference in these answers is
due to rounding). This is an important concept of time value of money.

Calculator Solution: 
Note: Intermediate answers are shown below as rounded, but the full answer was used to complete the calculation. 
Enter  
6.10%

$1
 
±$2
 
 
N
  
I/Y
  
PV
  
PMT
  
FV
 
Solve for 
11.71
    
Enter  
6.10%

$1
 
±$4
 
 
N
  
I/Y
  
PV
  
PMT
  
FV
 
Solve for 
23.41
    