Here are some resources that you might decide to use to extend your students' learning during this unit. I looked for activities for each grade level that would extend our students' understanding of concepts presented in the unit. They are listed below.
1st grade:
LOGIC: https://nrich.maths.org/7227
LOGIC: http://www.enchantedlearning.com/math/logic/puzzles/pets.shtml
ADDITION: http://www.openmiddle.com/equality-2-2/
COMPARING NUMBERS/ADDITION GAME: https://www.gregtangmath.com/howmany
ADDITION: The Very Hungry Caterpillar
GAME: 123 Nim
LESSON: Domino Sorting
2nd grade:
PROBLEM SOLVING: https://nrich.maths.org/1005
MATH ARGUMENTATION: https://nrich.maths.org/7383
GRAPHING: http://www.openmiddle.com/interpreting-data-2/
COINS GAME: https://www.gregtangmath.com/coinbubble
LESSON: 2,4,6 Puzzle
PUZZLE: Flower Petal Puzzles
3rd grade:
TIME: https://illuminations.nctm.org/Lesson.aspx?id=2328
ELAPSED TIME: https://illuminations.nctm.org/Lesson.aspx?id=3966
MULTIPLICATION: https://nrich.maths.org/1252
TIME: https://nrich.maths.org/1002/note
TIME: http://www.openmiddle.com/operations-with-time-2/
4th grade:
PLACE VALUE: https://nrich.maths.org/5950/note
PLACE VALUE: https://nrich.maths.org/2006/note
PLACE VALUE: http://wild.maths.org/tags/number-bases
SUBTRACTION: http://www.openmiddle.com/subtracting-multi-digit-numbers/
PERIMETER: http://www.openmiddle.com/rectangles-maximizing-perimeter/
PERIMETER/AREA: http://www.openmiddle.com/squares-perimeter-v-area/
GRAPHS: https://illuminations.nctm.org/Lesson.aspx?id=754
5th grade:
MAKING BOXES: https://nrich.maths.org/89/note
AREA/PERIMETER: https://nrich.maths.org/7280/note
AREA/PERIMETER: https://illuminations.nctm.org/Lesson.aspx?id=3879
AREA/GEOMETRY: https://www.youcubed.org/tasks/youcubed-my-heart/
VOLUME: https://illuminations.nctm.org/Activity.aspx?id=4095
PUZZLES: Skyscraper Puzzles
VOLUME: https://illuminations.nctm.org/Activity.aspx?id=4095
PUZZLES: Skyscraper Puzzles