In: Economics
a)
Consider the given problem here if “i” be the nominal rate of interest and “n” be the number of compounding periods, => the annual effective rate of interest is given below.
=> Annual effective rate of interest = (1+i/n)^n – 1.
Now, if the accounts balance of “$200” become “$203.75” after 1 month, => its monthly compounding.
So, let’s assume that “x” be the effective monthly interest rate, => $200*(1+x) = $203.75, => 1+x = 203.75/200.
=> 1+x = 1.01875, => x = 0.01875, => x = 1.875%.
So, we the “annual effective rate of interest rate” is “x*12”, => “22.5%”.
So, we have “annual effective interest rate”, now we can derive the “nominal rate of interest” by using the above expression.
=> Annual effective rate of interest = (1+i/n)^n – 1, => 22.5% + 1 = (1+i/n)^n, => 1.225 = (1+i/n)^n.
=> (1+i/n)^n = 1.225, => (1+i/12)^12 = 1.225, => (1+i/12) = 1.225^(1/12) = 1.0 171.
=> 1 + i/12 = 1.0171, => i/12 = 1.0171 – 1 = 0.0171, => i = 0.0171*12 = 0.2052.
So, the nominal rate of interest is “i=20.52%”.
b)
Consider the 2nd case.
Now, if the accounts balance of “$200” become “$203.75” after 1 month, => its compounded 4 times a month.
So, let’s assume that “x” be the effective interest rate, => $200*(1+x)^4 = $203.75, => (1+x)^4 = 203.75/200.
=> (1+x) = 1.01875^(1/4) = 1.0047, => x = 0.0047, => x = 0.47%.
So, we the “annual effective rate of interest rate” is “x*4*12 = 0.0047*4*12=0.2256”, => “22.56%”.
So, we have “annual effective interest rate”, now we can derive the “nominal rate of interest” by using the above expression.
=> Annual effective rate of interest = (1+i/n)^n – 1, => 22.56% + 1 = (1+i/n)^n, => 1.2256 = (1+i/n)^n.
=> (1+i/48)^48 = 1.2256, => (1+i/48) = 1.2256^(1/48) = 1.0042.
=> 1 + i/48 = 1.0042, => i/48 = 1.0042 – 1 = 0.0042, => i = 0.0042*12 = 0.2016.
So, the nominal rate of interest is “i=20.16%”.