pay back period

[Kake]

i am trying to work out the pay back period for the following:
b6 -80 000
b7 10 000
b8 40 000
b9 100 000

where b6 is the intal cost of the project, b7, b8, b9 represent what the
project returns after 1year 2 years 3years respectively. through working it
out on paper the pay back period for it is 2 years and 16 weeks that was
found by adding the 10 000 and the 40 000 together and minusing that from the
initial value then dividing what is left by the 3 years return and multipling
it by 52 to get weeks. however i have muliptle other columns with different
values and was wondering whether there was just one equation where it could
do it all for me.... any Suggestions???? thanks for any help in advance....

 

[Mike H]

A formula that does that could be done but it would give an incorrect answer
because it takes no account of where the 80000(£/$) came from in the first
place and what interest it is accruing until it is repaid.

Mike

 

[JLatham]

Barring things like the cost of money, I provided a general formula that did
what you did to get your 16 weeks in the duplicate posting here:
http://www.microsoft.com/office/com...0318f0-5f63-44d8-9a0b-556b94c83aa1&sloc=en-us

That formula will be as accurate (or inaccurate) as what you did by hand,
but it shows you how to use the same procedure referencing cells rather than
values so that you can use it elsewhere on a sheet with different sets of
numbers.