How long would it take $3,100 to grow to $8,200 if the annual rate is 3.6% and interest in compounded monthly

Principal amount (P) = $3100
Final amount  (A) = $8200
Interest rate (r) = 3.6% = 0.036
Interest is compounded monthly. So n = 12

Now we can apply compound interest formula as

Where t is time
Now we can place the value of A , P , r and n

Now we can simplify it as



On taking logarithmic function(ln) on both sides

Now we can use basic property of ln function as
So we can above expression as



So

32.10 is the correct answer