Pentertain by Ken de Courcy

From the introduction:

Here is a short, entertaining act that can be worked impromptu anywhere you have a pen, paper and audience. For larger shows it can be done with chalk and blackboard. I have even done it on an Overhead Projector during a break in a Training Course.

Introduction
PENTERTAIN
THE REQUIREMENTS
THE PREPARATION
THE FORMAT
Only Heaven (and Einstein) Knows!
Everything is Relative
A Not-so-Proper Charlie
The Chinese Check
The Forgotten Phone Number
A Question of Degree
A Last Word