# Thread: I think this is a calculus problem.... any advice?

1. ## I think this is a calculus problem.... any advice?

Hi everyone!

I have a little problem here that I am trying to work out but I can't solve... Really the problem here is that I'm a terrible Mathematicain! But I'm here to learn!!!!

The problem is simple (or at lease simply explained) and I have included a piece of a larger table (attached xls) that has all the informatio.

I run a comic book shop and I am developing a website for selling the comics. Unfortunately I have to input the prices of the comics manually. My web developer has made things easier for me by creating a program that allows me to input the prices. Now, there is a price guide that I am using but there are some problems. First of all, there are 17 different grades for the comics (ie, NM+, mn, mn- vf+, vf,vf-) and so on. Now, the guide lists the prices in NM-, VF, f, VG and G. When I looked closely at the prices I realised that there was not a constant relationship between the values. For example, when a comic is valued at $3 NM-, the price of the same comic in the condition VF is 66% of the NM- price. But when the comic is priced at$100 NM- the VF price is only 45% of this value.

The table below states the different values of NM-, beneath that is the percentage (expressed in decimal form) of that value. So what I was looking for was a formula to determine the percentages of the lower grades when the NM- value is input. The goal is to be able to integrate this formula into my website so I can accurately price all the comics.

If anyone could show me how to solve this problem or even point me in the right direction I would be truly grateful as it would be a tremendous help!!!

 NM- 3 5 8 10 15 25 30 40 50 60 65 75 90 105 VF 0.66 0.64 0.625 0.6 0.6 0.56 0.5333 0.5 0.48 0.46666 0.4615 0.4533 0.45555 0.4476 F 0.46 0.46 0.45 0.45 0.4 0.36 0.3 0.225 0.24 0.0234 0.2307 0.2133 0.2 0.2 VG 0.265 0.25 0.25 0.25 0.245 0.24 0.2 0.15 0.16 0.155 0.15 0.14666 0.133 0.1333333 G 0.13 0.127 0.125 0.125 0.1225 0.12 0.1 0.075 0.08 0.0782 0.0769 0.07333 0.07222 0.0666666

2. ## Re: I think this is a calculus problem.... any advice?

I don't think you will find a simple formula that connects all these cases together. If I were doing the pricing, I would just use linear interpolation based on the values in your table. For example, if you have a comic priced at 70 for NM-, then the adjustment for VF should be half way between 0.4615 and 0.4533, since 70 is half way between 65 and 75.

I suppose there is a way to automate this computation in Excel.

That's assuming I understand your problem correctly, which I may not.