How to display form submitted values without storing in database
I suggest:


deleting all the default submit handlers in the submit array in the $form variable - to stop the data being stored in the database
add your own submit handler to do the calculation and store the result in the standard PHP _SESSION variable
add a #redirect property in the (correct place) $form array variable to redirect the to URL of the result page
write code for the result page output the result in the _SESSION variable. To do this determine what type of page will display the result so that you can implement appropriate code to display the result  - there are several ways to do it: e.g. code in a template file, or a custom programmatically created block