I am trying to create a webform that has all the usual contact fields plus a field for visitors to add a number.

When the visitor fills out the fields and clicks submit, I would 70% of that number to be displayed.

So for example, if the number added to the webform field is 100, then after submitting the form the number 70 is displayed.

Is this possible?

I have looked at https://www.drupal.org/project/views_calc and https://www.drupal.org/project/webform_calculator and wonder which is best and if anyone has any other suggestions.

Thanks for your help,

Mike