Ability to show overall percentage

I need to show a feedback form where the clients can answer on a scale of 1-5 how we were rated on multiple tasks we completed for them.

I would like this to be sent back on the mail as a percentage. For example if there was 10 questions and they answered 5 of my questions with 4/5 and 5 questions 5/5 it would let me know they’d scored me 90% in total. Any ideas…?