SOLUTION: I have been pounding my head for 2 days trying to figure out the right equation for this problem and I am hoping someone here can help. What is the amount a person would have to

Algebra ->  Functions -> SOLUTION: I have been pounding my head for 2 days trying to figure out the right equation for this problem and I am hoping someone here can help. What is the amount a person would have to      Log On


   



Question 923755: I have been pounding my head for 2 days trying to figure out the right equation for this problem and I am hoping someone here can help.
What is the amount a person would have to deposit today to be able to take out $5000 a year for 10 years from an account earning 8 percent annually?
Thanks!

Found 2 solutions by josgarithmetic, KMST:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
p, amount to deposit today.

YEAR_________________BAL
0___________________p(1.08)^0
1___________________p(1.08)^1
2___________________p(1.08)^2
y___________________p(1.08)^y

Your question asks, p%281.08%29%5E10=5000 to find p.

Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
The way I understand it you want to know how much money should be deposited at time = 0 years,
into an account earning 8 percent annually,
so that at t=1 year, t=2 years, ..., t=8 years,
there would be at least $5000 that can be taken out.
At t=0 , balance%5B0%5D+=+A .
At t=1 (at the end of the first year) 8% interest ( 0.08A is added to the balance,
bringing the balance up to A%2B0.08A=1.08A ,
and immediately, 5000 is taken out,
bringing the balance down to balance%5B1%5D=1.08A-5000
At t=2 , balance%5B1%5D is again
increased by a factor of 1.08 ,
and reduced by the withdrawal of 5000 , so
.
At t=3 , balance%5B2%5D is again
increased by a factor of 1.08 ,
and reduced by the withdrawal of 5000 , so
.
This pattern repeats every year, and
at t=10 ,

If at that point balance%5B10%5D=0 ,

A%2A1.08%5E10=5000%2A%28%281.08%5E10-1%29%2F%281.08-1%29%29
A%2A1.08%5E10=5000%2A%28%281.08%5E10-1%29%2F0.08%29
A=5000%2A%281.08%5E10-1%29%2F%280.08%2A1.08%5E10%29
A=28733.19

NOTE:
The sum SUM=1.08%5E9%2B1.08%5E8%2B1.08%5E7%2B+%22...%22+%2B1.08%5E2%2B1.08%2B1
is the sum of a geometric sequence with ratio 1.08 .
You may know a formula for that, but otherwise you can see that
1.08%2ASUM=1.08%5E10%2B1.08%5E9%2B1.08%5E8%2B1.08%5E7%2B+%22...%22+%2B1.08%5E2%2B1.08 , and then
1.08%2ASUM-SUM=1.08%5E10-1--->%281.08-1%29%2ASUM=1.08%5E10-1--->SUM=%281.08%5E10-1%29%2F%281.08-1%29