Math Activity to Teach Doubling: Spinning for Doubles

Math Activity: Spinning for Doubles

Strand: Number Sense and Numeration, Addition & Multiplication
Math Strategy: Doubling

English:

French:

Materials:
• a copy of the board game and spinner
• counters, a pencil,
• a paper clip
• 2 players

Overview:
During this game students develop their understanding of the making doubles strategy as they work to find all the doubles needed to fill their game board. They take turns spinning the spinner; once the spinner stops, the student needs to identify what the double of that number is and place a counter on their side of the game board.  The players continue taking turns until one of them fills their entire game board.

How this Supports Student Learning: 
This game provides students an opportunity to practice learning their doubles.  Learning their doubles is an important milestone towards adding and multiplication.  Once students know their doubles, they can are quickly able to recognize near doubles and doubles plus one. This allows students to work with numbers flexibly, as they adjust numbers to make them easier to work with.

Where to next?
Concentrating on Doubles, Magic-Doubles, Over-Easy Doubles and Last One to School are all games that support the making doubles strategy. Practice with a variety of games will help the student to develop mastery of this strategy. Once the student is confident with making doubles you can introduce games that support the near doubles strategy, like Snappy Doubles, Find a Friendly Neighbour and Spinning for Near-Doubles.

These activities can be found, beginning on page 72, in the English Guide to Effective Instruction in Math Volume 5 https://bit.ly/2FNcQju and in the French Guide d'enseignement efficace des mathématiques, de la maternelle à la 6e année:Fascicule 5 on page 74-77 here.

Math Strategy: Doubling and Halving

Math Strategy: Doubling and Halving
Math Strand: Number sense and numeration

Location on the Continuum:


Overview:
Doubling and Halving is a multiplication strategy where a student will create a simpler problem by doubling one factor and halving the other. For example, to solve 18 x 15 a student might:


Halving and doubling can also be represented using an array model. For example, 4x4 can be modelled using square tiles arranged in an array. Without changing the number of tiles, the tiles can be rearranged to form a 2x8 array.



The halving-and-doubling strategy is practical for many types of multiplication problems that students in the junior grades will experience. The associative property can be used to illustrate how the strategy works.

26×5=(13×2)×5

= 13×(2×5)

= 13 × 10

= 1300


In some cases, the halving-and-doubling process can be applied more than once to simplify a multiplication expression.

12×15=6×30

= 3×60

= 180


Where to next?
When students are comfortable with halving and doubling, carefully planned activities will help them to generalize the strategy – that is, multiplying one number in the multiplication expression by a factor, and dividing the other number in the expression by the same factor, results in the same product as that for the original expression.



Source: A Guide to Effective Instruction in Mathematics, Kindergarten to Grade 6: Number Sense and Numeration, Grades 4 to 6 Volume 3 Multiplication

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