Math Activity to Teach Skip Counting: Target 75

Math Activity:  Target 75 

Math Strand:  Number Sense and Numeration
Math Strategy:  Skip Counting 
Key Idea: Unitizing

Materials:  
one die, paper and pencil

Overview:
This activity is found the Alex Lawson’s “What To Look For” on page 188.
After 6 turns, students are trying to have a total close to 75 without going over.

Students will roll a die and select a factor to multiply by:  1, 2, 3, 4, 5 or 10.
The game will encourage students to think about which number to select to multiply by so they are get as close to 75 as possible.

How this activity supports student learning?
Target 75 helps students make sense of quantity and the numbers they are using.

Students will begin to realize that if they select a higher factor in the beginning, they will need to use smaller ones and adjust their choices accordingly as the game goes on. For example, during their final rolls, they will need to decide between multiplying by 1 or 2 to get as close to 75 as possible. 

Students may play the game with a partner.  This encourages them to communicate with each other their mathematical thinking and reasoning. (e.g. It's our first roll, we should multiply the 5 by 10!  That equals 50.  We will be close to 75.) 

This game supports students understand of unitizing, which is the idea that objects can simultaneously be viewed as individual objects and as a composite unit that can be counted.    Through game play, students may use direct modelling to solve the problems, such as making 3 groups of 4 objects, then counting each object.  Moving beyond counting by ones, children may begin to rhythmically count the groups or they may repeatedly count groups on their fingers. This will then move to skip counting, then doubling, repeated addition or even a ratio table.



Students can use rekenreks, hundreds charts, number lines, counters or colour tiles  to help support their calculations. 



Where to next?
Challenge students to work with numbers larger than 75 or change the factors (e.g. 1, 5,6,7,8,9,10 ). 

Another game to try is Multiplication Challenge.

If students are not yet ready for all these factors  1,2,3,4,5,6, reduce the number of choices (Alter the Die by using masking tape or switch to number cards)