This math question can't be very hard, right?

[Monk]

If we assume that we use 15% more money on something every year from 1978 to 1987, how do we figure out the total increase during the time span?

[Asher]

Very simple.

Money = (StartMoney X (1.15)^{# of years}) - StartMoney

[Monk]

Thank you sir, that was most welcome.

[*End Is Forever*]

You've had that "world leader" a bit long Monk dear boy...

[Monk]

Hello there old chap! How are things? I figure no harm will be done threadjacking this one.

I am absolute incapable of finding or creating avatars, so I'm stuck with whatever I've got until Stefu's mercy provides another. You're absolutely right though, I have to find another trendy leader.

[*End Is Forever*]

Hmm... who's trendy enough to be in a Monk avatar?

[Dauphin]

I give you the President of Kazahkstan.




Find more leaders (as of 2000) here:

http://edition.cnn.com/2000/US/09/05/un.summit.names.reut/

[Monk]

Erm... don't tell anybody, but I've always liked Joschka Fischer, I think he seems like a genuinely cool dude. Then again, my German friend (a CSU supporter) tells me I'd think differently if I had a clue. What led you to that avatar?

[Dauphin]

I like this one, the PM of Chad.



He has a mad stare there.

[Harovan]

Isn't the answer rather

StartMoney * (1 + 1.15 + 1.15² + 1.15³ + ... + 1.15⁹ - 10) ?

This is not what Asher wrote, or did I understand the problem wrong. For example, you spend 1000 in 1978, 1150 in 1979, 1322.50 in 1980 etc. and you ask, how many more than 1000 per year you spent in the end? If so, Ashers solution sounds wrong.

[Monk]

Wow, the Kazahk Prez. You know what, that could work. I'm checking out a couple others right now, thanks a lot for the link.

[Monk]

Aaaah, no, Sir Ralph!

Why'd you have to go and make things so complicated?

Your interpretation is, I think, correct, though I can't say if your answer is. But now I'm confusing myself and probably the rest of you too.

[Dauphin]

Originally posted by Sir Ralph
Isn't the answer rather

StartMoney * (1 + 1.15 + 1.15² + 1.15³ + ... + 1.15⁹ - 10) ?

This is not what Asher wrote, or did I understand the problem wrong. For example, you spend 1000 in 1978, 1150 in 1979, 1322.50 in 1980 etc. and you ask, how many more than 1000 per year you spent in the end? If so, Ashers solution sounds wrong.

The increase is what Asher wrote. The cumulative increase is what you have written. Not sure which Monk was after though.

[Harovan]

If my interpretation is correct, the my solution should be correct too. In this case, the solution is

SUM^{(n from 0 to 9)}(1.15ⁿ) - SUM^{(n from 0 to 9)}(1)

The former term is 1 + 1.15 + 1.15² ..., the latter term is 10.

[Spiffor]

Monk :
Who's on your avatar ?

Others :
Can you continue the following pattern ?

1
11
21
1211
111221
312211
13112221