Financial math compound

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Billy Bob, who is 22, won a prize of $5000 at McDonalds. He invests the money at
8% compounded quarterly for 43 years until he retires. When he retires, he then
reinvests the money at 7% compounded monthly and makes equal monthly
withdrawals for a further 25 years at which time the money would run out. How
much money would he get each month? Show all work



This is how I answered:
FV = R (1+i)^n = 5000(1+0.02)^172 where i=0.08/4 and n=43*4
FV = $150729.9473



Then:
PV= P [(1 + i)^n]- 1 / [1 + i]^n/i where i=0.07/12 and n = 24*12
$150729.9473 = P [(1 + 0.07/12)^24*12]-1 / [1+0.07/1]^24*12/0.07/12
P= $150729.9473 / 141.48690338
P = $1,065.33



However the answer should be 1,044.74 . I think I am doing something wrong with the interest. I know my answer is very close to the right answer but it is still incorrect.







share|cite|improve this question



















  • In your first equation, shouldn't the interest be 0.08, and not 0.02 in $R(1+i) = 5000(1+0.08)^172$?
    – amWhy
    Jul 15 at 19:43







  • 1




    In the second part, shouldn't $n=25times 12$?
    – lulu
    Jul 15 at 19:45






  • 1




    Worth noting: your formulas are nearly unreadable. here is a good tutorial for formatting on this site.
    – lulu
    Jul 15 at 19:53










  • I think you have calculated $141.48690338$ as $left dfrac1-frac 1 [1+0.07/12]^25*120.07/12 right$ but this is not what I think you have written
    – Henry
    Jul 15 at 21:14










  • you'll have the result $1,044.74$ if $7%$ is the effective annual interest, so that the monthly interest is $i_m=1.07^1/12-1approx 0.57%$.
    – alexjo
    Jul 15 at 21:49














up vote
1
down vote

favorite












Billy Bob, who is 22, won a prize of $5000 at McDonalds. He invests the money at
8% compounded quarterly for 43 years until he retires. When he retires, he then
reinvests the money at 7% compounded monthly and makes equal monthly
withdrawals for a further 25 years at which time the money would run out. How
much money would he get each month? Show all work



This is how I answered:
FV = R (1+i)^n = 5000(1+0.02)^172 where i=0.08/4 and n=43*4
FV = $150729.9473



Then:
PV= P [(1 + i)^n]- 1 / [1 + i]^n/i where i=0.07/12 and n = 24*12
$150729.9473 = P [(1 + 0.07/12)^24*12]-1 / [1+0.07/1]^24*12/0.07/12
P= $150729.9473 / 141.48690338
P = $1,065.33



However the answer should be 1,044.74 . I think I am doing something wrong with the interest. I know my answer is very close to the right answer but it is still incorrect.







share|cite|improve this question



















  • In your first equation, shouldn't the interest be 0.08, and not 0.02 in $R(1+i) = 5000(1+0.08)^172$?
    – amWhy
    Jul 15 at 19:43







  • 1




    In the second part, shouldn't $n=25times 12$?
    – lulu
    Jul 15 at 19:45






  • 1




    Worth noting: your formulas are nearly unreadable. here is a good tutorial for formatting on this site.
    – lulu
    Jul 15 at 19:53










  • I think you have calculated $141.48690338$ as $left dfrac1-frac 1 [1+0.07/12]^25*120.07/12 right$ but this is not what I think you have written
    – Henry
    Jul 15 at 21:14










  • you'll have the result $1,044.74$ if $7%$ is the effective annual interest, so that the monthly interest is $i_m=1.07^1/12-1approx 0.57%$.
    – alexjo
    Jul 15 at 21:49












up vote
1
down vote

favorite









up vote
1
down vote

favorite











Billy Bob, who is 22, won a prize of $5000 at McDonalds. He invests the money at
8% compounded quarterly for 43 years until he retires. When he retires, he then
reinvests the money at 7% compounded monthly and makes equal monthly
withdrawals for a further 25 years at which time the money would run out. How
much money would he get each month? Show all work



This is how I answered:
FV = R (1+i)^n = 5000(1+0.02)^172 where i=0.08/4 and n=43*4
FV = $150729.9473



Then:
PV= P [(1 + i)^n]- 1 / [1 + i]^n/i where i=0.07/12 and n = 24*12
$150729.9473 = P [(1 + 0.07/12)^24*12]-1 / [1+0.07/1]^24*12/0.07/12
P= $150729.9473 / 141.48690338
P = $1,065.33



However the answer should be 1,044.74 . I think I am doing something wrong with the interest. I know my answer is very close to the right answer but it is still incorrect.







share|cite|improve this question











Billy Bob, who is 22, won a prize of $5000 at McDonalds. He invests the money at
8% compounded quarterly for 43 years until he retires. When he retires, he then
reinvests the money at 7% compounded monthly and makes equal monthly
withdrawals for a further 25 years at which time the money would run out. How
much money would he get each month? Show all work



This is how I answered:
FV = R (1+i)^n = 5000(1+0.02)^172 where i=0.08/4 and n=43*4
FV = $150729.9473



Then:
PV= P [(1 + i)^n]- 1 / [1 + i]^n/i where i=0.07/12 and n = 24*12
$150729.9473 = P [(1 + 0.07/12)^24*12]-1 / [1+0.07/1]^24*12/0.07/12
P= $150729.9473 / 141.48690338
P = $1,065.33



However the answer should be 1,044.74 . I think I am doing something wrong with the interest. I know my answer is very close to the right answer but it is still incorrect.









share|cite|improve this question










share|cite|improve this question




share|cite|improve this question









asked Jul 15 at 19:39









AneQo

284




284











  • In your first equation, shouldn't the interest be 0.08, and not 0.02 in $R(1+i) = 5000(1+0.08)^172$?
    – amWhy
    Jul 15 at 19:43







  • 1




    In the second part, shouldn't $n=25times 12$?
    – lulu
    Jul 15 at 19:45






  • 1




    Worth noting: your formulas are nearly unreadable. here is a good tutorial for formatting on this site.
    – lulu
    Jul 15 at 19:53










  • I think you have calculated $141.48690338$ as $left dfrac1-frac 1 [1+0.07/12]^25*120.07/12 right$ but this is not what I think you have written
    – Henry
    Jul 15 at 21:14










  • you'll have the result $1,044.74$ if $7%$ is the effective annual interest, so that the monthly interest is $i_m=1.07^1/12-1approx 0.57%$.
    – alexjo
    Jul 15 at 21:49
















  • In your first equation, shouldn't the interest be 0.08, and not 0.02 in $R(1+i) = 5000(1+0.08)^172$?
    – amWhy
    Jul 15 at 19:43







  • 1




    In the second part, shouldn't $n=25times 12$?
    – lulu
    Jul 15 at 19:45






  • 1




    Worth noting: your formulas are nearly unreadable. here is a good tutorial for formatting on this site.
    – lulu
    Jul 15 at 19:53










  • I think you have calculated $141.48690338$ as $left dfrac1-frac 1 [1+0.07/12]^25*120.07/12 right$ but this is not what I think you have written
    – Henry
    Jul 15 at 21:14










  • you'll have the result $1,044.74$ if $7%$ is the effective annual interest, so that the monthly interest is $i_m=1.07^1/12-1approx 0.57%$.
    – alexjo
    Jul 15 at 21:49















In your first equation, shouldn't the interest be 0.08, and not 0.02 in $R(1+i) = 5000(1+0.08)^172$?
– amWhy
Jul 15 at 19:43





In your first equation, shouldn't the interest be 0.08, and not 0.02 in $R(1+i) = 5000(1+0.08)^172$?
– amWhy
Jul 15 at 19:43





1




1




In the second part, shouldn't $n=25times 12$?
– lulu
Jul 15 at 19:45




In the second part, shouldn't $n=25times 12$?
– lulu
Jul 15 at 19:45




1




1




Worth noting: your formulas are nearly unreadable. here is a good tutorial for formatting on this site.
– lulu
Jul 15 at 19:53




Worth noting: your formulas are nearly unreadable. here is a good tutorial for formatting on this site.
– lulu
Jul 15 at 19:53












I think you have calculated $141.48690338$ as $left dfrac1-frac 1 [1+0.07/12]^25*120.07/12 right$ but this is not what I think you have written
– Henry
Jul 15 at 21:14




I think you have calculated $141.48690338$ as $left dfrac1-frac 1 [1+0.07/12]^25*120.07/12 right$ but this is not what I think you have written
– Henry
Jul 15 at 21:14












you'll have the result $1,044.74$ if $7%$ is the effective annual interest, so that the monthly interest is $i_m=1.07^1/12-1approx 0.57%$.
– alexjo
Jul 15 at 21:49




you'll have the result $1,044.74$ if $7%$ is the effective annual interest, so that the monthly interest is $i_m=1.07^1/12-1approx 0.57%$.
– alexjo
Jul 15 at 21:49










1 Answer
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If I´m right in total your equality was more or less



$$5000cdot 1.02^43cdot 4cdot (1+frac0.0712)^25cdot 12=Pcdot frac(1+0.07/12)^25cdot 12-1frac0.0712$$



As lulu has already mentioned, it has to be $25cdot 12$. But nevertheless I get the same result, $P=1065.33$. See here the result of the calculator w.a. And I agree with your calculation. I don´t see any mistake.




After testing other variations I´ve found out that they have used the $texttteffective interest rate$ (aka equivalent interest rate) for the $7%$.



To get the equivalent interest rate one has to solve the fowing equation



$left(1+fraci12 right)^12=1.07 Rightarrow i=(1.07^1/12-1)cdot 12=0.06784974465$



If you replace $0.07$ by the equivalent interest rate you´ll get the desired solution: calculator w.a. I think a little less number of digits is sufficient.






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    1 Answer
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    1 Answer
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    up vote
    1
    down vote



    accepted










    If I´m right in total your equality was more or less



    $$5000cdot 1.02^43cdot 4cdot (1+frac0.0712)^25cdot 12=Pcdot frac(1+0.07/12)^25cdot 12-1frac0.0712$$



    As lulu has already mentioned, it has to be $25cdot 12$. But nevertheless I get the same result, $P=1065.33$. See here the result of the calculator w.a. And I agree with your calculation. I don´t see any mistake.




    After testing other variations I´ve found out that they have used the $texttteffective interest rate$ (aka equivalent interest rate) for the $7%$.



    To get the equivalent interest rate one has to solve the fowing equation



    $left(1+fraci12 right)^12=1.07 Rightarrow i=(1.07^1/12-1)cdot 12=0.06784974465$



    If you replace $0.07$ by the equivalent interest rate you´ll get the desired solution: calculator w.a. I think a little less number of digits is sufficient.






    share|cite|improve this answer



























      up vote
      1
      down vote



      accepted










      If I´m right in total your equality was more or less



      $$5000cdot 1.02^43cdot 4cdot (1+frac0.0712)^25cdot 12=Pcdot frac(1+0.07/12)^25cdot 12-1frac0.0712$$



      As lulu has already mentioned, it has to be $25cdot 12$. But nevertheless I get the same result, $P=1065.33$. See here the result of the calculator w.a. And I agree with your calculation. I don´t see any mistake.




      After testing other variations I´ve found out that they have used the $texttteffective interest rate$ (aka equivalent interest rate) for the $7%$.



      To get the equivalent interest rate one has to solve the fowing equation



      $left(1+fraci12 right)^12=1.07 Rightarrow i=(1.07^1/12-1)cdot 12=0.06784974465$



      If you replace $0.07$ by the equivalent interest rate you´ll get the desired solution: calculator w.a. I think a little less number of digits is sufficient.






      share|cite|improve this answer

























        up vote
        1
        down vote



        accepted







        up vote
        1
        down vote



        accepted






        If I´m right in total your equality was more or less



        $$5000cdot 1.02^43cdot 4cdot (1+frac0.0712)^25cdot 12=Pcdot frac(1+0.07/12)^25cdot 12-1frac0.0712$$



        As lulu has already mentioned, it has to be $25cdot 12$. But nevertheless I get the same result, $P=1065.33$. See here the result of the calculator w.a. And I agree with your calculation. I don´t see any mistake.




        After testing other variations I´ve found out that they have used the $texttteffective interest rate$ (aka equivalent interest rate) for the $7%$.



        To get the equivalent interest rate one has to solve the fowing equation



        $left(1+fraci12 right)^12=1.07 Rightarrow i=(1.07^1/12-1)cdot 12=0.06784974465$



        If you replace $0.07$ by the equivalent interest rate you´ll get the desired solution: calculator w.a. I think a little less number of digits is sufficient.






        share|cite|improve this answer















        If I´m right in total your equality was more or less



        $$5000cdot 1.02^43cdot 4cdot (1+frac0.0712)^25cdot 12=Pcdot frac(1+0.07/12)^25cdot 12-1frac0.0712$$



        As lulu has already mentioned, it has to be $25cdot 12$. But nevertheless I get the same result, $P=1065.33$. See here the result of the calculator w.a. And I agree with your calculation. I don´t see any mistake.




        After testing other variations I´ve found out that they have used the $texttteffective interest rate$ (aka equivalent interest rate) for the $7%$.



        To get the equivalent interest rate one has to solve the fowing equation



        $left(1+fraci12 right)^12=1.07 Rightarrow i=(1.07^1/12-1)cdot 12=0.06784974465$



        If you replace $0.07$ by the equivalent interest rate you´ll get the desired solution: calculator w.a. I think a little less number of digits is sufficient.







        share|cite|improve this answer















        share|cite|improve this answer



        share|cite|improve this answer








        edited Jul 15 at 21:58


























        answered Jul 15 at 21:17









        callculus

        16.4k31427




        16.4k31427






















             

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