Calculating Cost/Pallet for 5 Months: Terminology & Formula

[briandewyea]

Hi,
I am working on building some excel spreadsheets, and need to know the terminology for a math process to help with building formulas. This is the situation I'm working on:
I am charged \$10/pallet of goods per month.
I order 10 pallets of material, of which 2 pallets every month are consumed.
It will take 5 months to go through all my stock.

My question is: What is the term called to figure this out? I know it's 10+8+6+4+2=30...so it will cost \$300 in storage...but I don't know what it's called. Is there some sort of formula I can use, rather than doing it long-hand?

Thanks!

 

[Joppy]

I'm guessing the amount of pallets ordered and sold each month is different? If not, you've answered all the questions you need to.

 

[Opalg]

My question is: What is the term called to figure this out? I know it's 10+8+6+4+2=30...so it will cost \$300 in storage...but I don't know what it's called. Is there some sort of formula I can use, rather than doing it long-hand?

A sequence of numbers that increase or decrease at a constant rate, like 10,8,6,4,2, is called an arithmetic progression. The link in the previous sentence will give you a formula for the sum of the series. The easiest way to state the formula is that you add the first and last terms, multiply by the number of terms, then divide by 2. In the case of your series, that would give $\dfrac{(10+2)\times5}2 = \dfrac{60}2 = 30.$

 

[briandewyea]

Joppy - Correct, we're continually getting various numbers of pallets of parts that have different amounts on them, all of which are worked down to 0 at different rates

Opalg - Thanks so much! I'll use this link and work that into my spreadsheet. This is exactly what I was looking for!