Question 5
Consider the $5\times5$ geoboard. The two illustrated crosses each surround five pins.
A. Find every square surrounding nine pins.
A closed shape can also use 24 pins: start at a pin, move to the next pin horizontally or vertically, visit each pin at most once, and return to the starting pin. Two examples are shown.
Some pins are always part of any such 24-pin shape; one is marked below.
B. Find all such compulsory pins.
A. Find every square surrounding nine pins.
A closed shape can also use 24 pins: start at a pin, move to the next pin horizontally or vertically, visit each pin at most once, and return to the starting pin. Two examples are shown.
Some pins are always part of any such 24-pin shape; one is marked below.
B. Find all such compulsory pins.