Why is this so hard for me???

[Afrotech]

Here is my problem:

I have been asked to show how I came up with a projection by using a formula... problem is, I'm having trouble coming up with the formula.

Here is what I am doing:

Each of our customers sell .83 products a month. We are starting our projection with 100 customers. We hope to add 100 customers each month. So, after month 1 we will have sold 83 units (.83*100).

I know that in month 2 we have 200 courses now, 100 sold 83 the first month and 83 the second, so the first 100 courses sold a total of 166 units by month 2 and the added 100 coures sold 83 so by the end of month 2 we have sold 249.

What's the formula?

This is what happens only 2 years after you graduate college

 

[Afrotech]

no one?

 

[Kelemvor]

Basically adding up all the numbers from 1 to whatever month you are dealing with and then multiplying that by .83? Does the n! thing mean addition or multiplication? hmm.

 

[amish]

.83((X-1)100) + .83(100X)

where X = what month you are in


EDIT: i shouldn't have told you this if their was only a 5% chance that you would like me.

 

[njmodi]

Let n = be the total number of months you are trying to calculate for:

The formula is (Sum of 0, 1, 2, ..n) * (100 * 0.83) = Sum(0,n)*83

This can be expressed as: (n(n+1))/2 * 83

In your case:

Month 1, n = 1 => (1(1+1))/2 * 83 = 2/2 * 83 = 1 * 83 = 83
Month 2, n = 2 => (2(2+1))/2 * 83 = 6/2 * 83 = 3 * 83 = 249

And so on.

 

[njmodi]

Originally posted by: FrankyJunior
Basically adding up all the numbers from 1 to whatever month you are dealing with and then multiplying that by .83? Does the n! thing mean addition or multiplication? hmm.

Exactly - its not n! (factorial => 1*2*...*n)

The sum of all numbers (0...n) = n(n+1)/2

 

[Kelemvor]

Originally posted by: njmodi

Originally posted by: FrankyJunior
Basically adding up all the numbers from 1 to whatever month you are dealing with and then multiplying that by .83? Does the n! thing mean addition or multiplication? hmm.

Exactly - its not n! (factorial => 1*2*...*n)

The sum of all numbers (0...n) = n(n+1)/2

Yeah that's right. Couldn't remember what the ! thing stood for but knew it was one or the other.

 

[Afrotech]

Originally posted by: amish

EDIT: i shouldn't have told you this if their was only a 5% chance that you would like me.

Everyone who relied to my post is included in the 5%.... Lucky You!

 

[Juno]

Seek any math tutors.