Easier way of finding the principle investment in P = (PRT/100)..?

[Phavonic]

Hi,


Is there an easier way to calculate the principle investment when dealing with simple interest, for the example given below?


I find myself having to change the subject of this formula and so doing it the long way..


A = P + (PRT/100)


Where A is the total amount, P is the principle investment, and R the rate of interest per time T.


So for a question like....


Find the principle investment if the final amount after 4.25 years at an interest rate of %3.5 per annum is £68.50.


68.50 = {(P x 4.25 x 3.5) + (P x 100)}/ 100


68.50 x 100 = (P x 14.875) + (P x 100)


6850 = P(14.875 + 100)


6850 = P x 114.875


P = 6850/114.875


P = £59.63


But is there and easier way of doing such sums that I'm not seeing? Thanks.

 

[Phavonic]

The title should have read P + (PRT/100)

 

[lev888]

If A = P + (PRT/100), then P = ?

 

[Denis]

f = future value = 68.50
r = annual rate = 3.5/100 = .035
n = number of years = 4.25
p = present value = ?

Formula: p = f / (1 + n*r)

OK?

 

[Phavonic]

If A = P + (PRT/100), then P = ?

P = 100A/(RT + 100)...but can this be simplified?

 

[lev888]

P = 100A/(RT + 100)...but can this be simplified?

Why do you think there is something to simplify? It's not any more complicated than the original formula. Other than the 100 all of the terms are different.