Help me solve this formula!

[MatthewJF11]

Hi all,

I have been working through the formula below, however I cannot arrive at 142.9216.



I have tried 1) scientific calculator and 2) online algebra calculator - and I get 78.19, could you please advise where I am going wrong, or is the answer of 142.9216 simply wrong?

Your advice here is most welcome.

Kind regards,
Matthew

 

[Dr.Peterson]

I have been working through the formula below, however I cannot arrive at 142.9216.

View attachment 25222

I have tried 1) scientific calculator and 2) online algebra calculator - and I get 78.19, could you please advise where I am going wrong, or is the answer of 142.9216 simply wrong?

I can't tell where you went wrong without seeing what you did! What did you enter into the calculators?

I do get their answer, which I did using Excel for speed.

 

[Deleted member 4993]

Hi all,

I have been working through the formula below, however I cannot arrive at 142.9216.

View attachment 25222

I have tried 1) scientific calculator and 2) online algebra calculator - and I get 78.19, could you please advise where I am going wrong, or is the answer of 142.9216 simply wrong?

Your advice here is most welcome.

Kind regards,
Matthew

Your calculations must be incorrect. Just the second term:

100/(1 + 0.015)²⁰ ~ 100 * (1 + 0.015)^-20 ~ 100 * (1 - 0.015*20) ~ 70

So when we add the first term (Σ[4/(1+0.15)ⁿ] - t will be larger than ~ 100