Use the "rule of 72" to estimate the doubling time (in years) for the interest rate, and then calculate it exactly. (Round your answers to two decimal places.)7.3%compounded weekly.

"rule of 72" ___ ?

Exact Answer ___?

The rule of 72 is a shortcut to estimate the number of years required to double your money at a given annual rate of return. The rule states that you divide the rate, expressed as a percentage, into 72:

Years required to double investment = 72 compound annual interest rate Note that a compound annual return of 8% is plugged into this equation as 8, not 0.08

We are given the interest rate as 7.3% compounded weekly = 7.3/(52) , {Considering its a 52 week year}

=> Annual interest rate = 7.3/52

Years required to double investment = 72 compound annual interest rate = 72/(7.3/52)= 72*52/7.3 = 512.876 years

For the exact answer use the compound interest formula A =P(1+r/n)^(nt) here A = 2P , n=52 , r = 7.3/100

=> 2P = P(1+7.3/5200)^(52t) 2 = (1+7.3/5200)^(52t) take log with exponential base on both the sides => ln(2)= 52t*ln(1+7.3/5200)

t =ln(2)/[52*ln(1+7.3/5200)] t = 9.50 years

hence (RULE OF 72) = 512.88 yr

(EXACT ANSWER) = 9.50 yr

The following answers listed above were incorrect.