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The Lumenary
Darasa la 3–5Discrete MathematicsImepangwa

Dots and lines: networks and puzzles

Networks of dots joined by lines: tracing figures without lifting the pencil, finding routes, and counting how many lines meet at each dot.

math.discrete.networks-puzzles

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Utajifunza

  • Decide by experiment which figures can be traced in one stroke without retracing a line.
  • Count the line ends at each dot and notice the pattern behind traceable figures.
  • Find shortest routes in a small road network with distances marked.

Fasili

  • A network (graph) is a collection of dots (vertices) with lines (edges) joining some pairs of them.
  • The degree of a dot is the number of line ends at it.

Nadharia

  • The degrees of all the dots add up to an even number: twice the number of lines.
  • A connected figure can be traced in one stroke exactly when it has either no dots or exactly two dots of odd degree.

Mawazo potofu ya kawaida

  • Thinking whether a figure can be traced depends on its overall shape rather than on the degrees of its dots.
  • Believing the shortest route is always the one with the fewest roads.

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