# MATH!!!

posted by
**Anonymous**
.

an oil well produceds 2500 barrels of oil during its firt month of production. The oil company predicts its production will drop 5% each month thereafter. how many barrels of iol will this company produce in its first yeear?

what formula would I use and I how I do this question?

There's a slight interpretation problem with this question. It states

"an oil well produceds 2500 barrels of oil during its firt month of production. The oil company predicts its production will drop 5% each month thereafter. how many barrels of iol will this company produce in its first yeear?"

Does the 5% per month mean 5% of 2500 = 125 barrels, or does it mean 5% of the previous month's production? So it would go 125, 118.75, 112.8125,...i.e. a decreasing geometric sequence?

The answer will depend on what course/unit this is coming from.

If it's a geometric sequence then use the production in month n is 2500*.95^{n-1}

You should have some formula telling you how to add up the first n terms of a geometric sequence, check your text.

I saw this problem below and forgot to respond, sorry about that. I ususlly run through and look at all the unanswered questions relating to math, then answer them (provided no one else has done so) as I find them difficult, i.e. I like to find the hard ones first.

I still don't get what you are saying!

Ok, let's try again. What I'm saying is the answer will depend on how the production is decreasing, arithmetically or geometrically.

If you start with a production of 2500 barrels per month and it's decreasing arithmetically, then the sequence goes

2500, 2500-125, 2500-250, 2500-375,...2500-125*n

If the production is decreasing geometrically then it goes

2500, 2500*.95, 2500*.95^{2}, 2500*.95^{3}, 2500*.95^{4},..., 2500*.95^{n}

The answer will depend on the how we interpret the 5% decrease per month. I really don't know how I can make it any simpler. I checked the methods on a spreadsheet. If it's arithmetically, then the production for a year is 29280 barrels and if geometrically it's 22982 barrels.

What is it you're having trouble with?

okay so my question is you can do it either way and it is still correct? geometrically or arithmetically?

It's correct depending on how the answer is supposed to be solved. What unit are you studying right now, geometric sequences/series?

Both answer are correct "depending" on how we interpret the 5% per month decrease. The calculations are different, so it matters very much what the directions tell you to do.

I am learing both geometric sequences/series so that is why I am confused!

Ok, then most likely you're expected to think of the production as decreasing geometrically

These are the numbers I got on my spreadsheet

month

n...... production in barrels

__________________

1.......2500.0000

2.......2375.0000

3.......2256.2500

4.......2143.4375

5.......2036.2656

6.......1934.4523

7.......1837.7297

8.......1745.8432

9.......1658.5511

10......1575.6235

11......1496.8423

12......1422.0002

The total is 22981.9956 barrels, which rounds to 22982

The production in month n is 2500*.95^{n-1}

The sum for n months is given by (a-ar^{n})/(1-r) where a=2500 and r=.95

I'll try to help you. but this is not a teaching site, we try to help with homework. I'm not sure what it is that's confusing you. You must be aware that in word problems there are frequently different ways to interpret the problem; this is called ambiguity and we try very hard to eliminate it in math and science. This is not an unusual situation, so you need to be aware of it.

heelo!!!

iam from latvia and i don't good speak english.i don't understand homeworks maths!please can help me.?

sur but you have to post your on!

Well, you certainly spell very well for someone who doesn't know English well, so this looks very suspicious.

So, what's your question?... and you might want to click on the link that says Post a New Question above so we won't miss it.