Illustrative Mathematics Kindergarten, Unit 7: Measuring and Comparing Length and Weight
In this unit, your child compares objects by how long and how heavy they are. Kindergartners line things up from the same starting point to see which is longer, use a balance or their hands to tell heavier from lighter, and sort objects into groups and count them. After counting to 100, this connects math to real things, and the final unit brings the year's skills together.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 7?
- Describing objects by their length and weight, and noticing that a long object is not always a heavy one. Learn more: Describing how long or heavy things are
- Lining up objects from the same starting point to compare length, and using hands or a balance to compare weight. Learn more: Comparing which is longer, taller, or heavier
- Sorting objects by a feature, such as long and short, counting each group, and ordering the groups from most to fewest. Learn more: Sorting things into groups and counting them
Sample questions to try together
These are real questions from our practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
Is a feather heavy or light?
- Heavy
- Light
- Neither
How you can help
- Line up three shoes with their heels against a wall and ask your child which is longest and which is shortest.
- Hang two bags from the ends of a clothes hanger, put a different object in each, and let your child see which side dips lower.
- Sort toys into long and short groups at cleanup time, count each group, and ask your child which group has more.
Where kids can get stuck
- Lining up objects from different starting points, so the one placed further ahead looks longer.
- Thinking the higher side of a balance holds the heavier object.
- Assuming the longest object is also the heaviest, like a paper tube against a can of soup.
Practice makes perfect
Bobby's Math Club has practice problems that adapt to your child’s level, each with a detailed explanation and an easy-to-follow video, so your child can build confidence in these skills one step at a time.
Words your child will hear
- length
- How long something is from one end to the other.
- weight
- How heavy something is.
- longer
- Stretching further from end to end than something else.
- shorter
- Not as long or not as tall as something else.
- heavier
- Weighing more; harder to lift.
- lighter
- Weighing less; easier to lift.
- balance
- A tool that tips down on the heavier side to compare weights.
- sort
- To put things into groups that belong together.
Ready to build your child’s confidence with comparing length and weight?
In Bobby's Math Club, your child practices these skills at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free.
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Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
Which math standards does Illustrative Mathematics Kindergarten Unit 7 cover?
Illustrative Mathematics Kindergarten Unit 7 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
For teachers: Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence. Learn how Bobby's Math Club can help your students grow.