B1.5 Count to 50 by 1s, 2s, 5s, and 10s, using a variety of tools and strategies.
Skill: Skip Counting
Recognizing the pattern of numbers from 1 to 9 and understanding how it repeats throughout the base 10 numbering system, namely, tens, hundreds, thousands, etc., helps students count and understand the concept of place value and thus master the decimal system. Thus, patterns in multiples of numbers, such as all multiples of 5 ending in 5 or 0, help make a connection to divisibility (all numbers ending in 0 or 5 are divisible by 5, for example). Similarly, the regularity in even-numbered patterns (0, 2, 4, 6…) helps establish that the difference between two consecutive even numbers is always 2.
Source : Guide d’enseignement efficace des mathématiques de la 1re à la 3e année, p. 60.
To help students develop the skill of recognizing number order relationships, teachers may ask students to skip count up by 1 (28, 29, 30, 31…) or by intervals (2, 10, 15…) and to count backwards by 1 (11, 10, 9…) or by intervals (40, 30, 20…) from a given number.
These activities help students recognize that when counting by 1 or by intervals, any number named is greater than those before it and less than those after it, whereas when counting backwards by 1 or by intervals, any number named is less than those before it and greater than those after it. While these relationships seem obvious to adults, students often get them wrong because they do not consider the concept of grouping; for example, when asked to name the number before 40, many tend to spontaneously answer 49 because students focus on the 0; they know that a number ending in 0 is always preceded by a number ending in 9, and they forget to consider grouping by tens. In contrast, when the same problem is contextualized, students are more likely to give thoughtful responses; for example, in a situation where a child has 20 field hockey cards and loses one, students will readily respond that they have 19 cards left.
Using a homemade abacus or odometer (created with a toilet paper roll and template) helps students compare numbers, skip count, and discover changes related to tens groupings.
Source : Guide d’enseignement efficace des mathématiques de la 4e à la 6e année, p. 46-47.