For 19 you can get a line of symmetry between each one that is hand to hand (wing to wing) and each one that is nose to nose. Those total 7. In other words, you can make a fold in many places if you take two at a time (or individuals which is what the problem asks).

#### Geometry Introduction

The surfer/spotter problem of Geometry is answered on page 290 of the Enhanced Teachers Guide for Geometry by Jacobs (ISBN: 0716756072). Since we no longer...