Teaching Models

Fractions and Probability

Symmetry, Fractions, and Probability
A figure has symmetry if it can be folded so the two parts match exactly. Some children can visually identify symmetrical shapes; other children may need practice in folding and cutting out shapes and then refolding them to see that the parts match exactly. Children can also examine pictures and classroom objects to see if they have symmetry or not. Identifying lines of symmetry leads to discovering halves—objects or drawings with two congruent parts. Most children can relate the concept of finding “half” to sharing something equally with another person.

The study of two equal parts, or halves, leads to the fact that a shape can also be separated into three or more equal parts. Children learn to associate one-half with 1 of 2 equal parts of a figure. This is extended to the study of one-third and one-fourth as being one of 3 equal parts and 1 of 4 equal parts, respectively.

The concept of equal parts as used in symmetry and with fractions can be extended to a brief introduction to probability. At this grade level, children need only to understand that probability means what is most likely to happen. If a spinner is divided into two equal parts, the probability of spinning and having the pointer land on either part is equal. If one part is much larger than the other, the probability of the pointer landing on the larger part is greater than the probability of it landing on the smaller part.

Teaching Model 9.1: Equal Parts

Houghton Mifflin Math Grade 1