How to do calculation using a dropdown menu?

good morning

I am kind of looking to get some help on customizing a from.

for example

I would like a dropdown menu with lets say 4 items.

each item selected has a different price range.

now a math function should calculate with some other geo generated number just as km or miles.

how can I do this

You can assign the calculation values to the dropdown menu items so that these values can be used for calculation based on the selected item. 

Please refer to the guide below that can help you in performing calculations in the form.

http://www.jotform.com/help/259-How-to-perform-calculation-in-the-form

We have also integrated with several math functions in the calculation wizard that might help you in achieving your requirement.

Hope this information helps! Please get back to us if you need any further assistance. We will be happy to help.