1st Grade · Measurement & Data
1.MD.A.1: Order three objects by length
1.MD.A.1 is a 1st grade Common Core math standard in Measurement & Data. Here’s what it really covers, and how you can help your students learn it.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
The standard
Order three objects by length; compare the lengths of two objects indirectly by using a third object.
In plain words
Order three objects by length.
Sample questions from student practice
These questions from Bobby's Math Club are the kinds of questions your students will see. You can try answering them to see what a student might see.
Question 1 of 3
Which object is usually the longest?
- A book
- A bus
- A shoe
Where students can get stuck
- Comparing lengths without lining up the ends, so a shorter pencil that sticks out further looks longer.
- Placing the third object in the wrong spot, putting the middle-length item at one end of the row.
- Ignoring what the string shows and insisting one item is longer because it looks bigger or thicker.
Effective teaching strategies
- Line up three objects with their left ends at the same starting line, including one short thick object and one long thin object, and have students order them from shortest to longest.
- Mark a paper strip to match a bookshelf that cannot be moved, carry the strip to a table, and ask students which is longer, the table or the bookshelf, and how the strip shows it.
- Place three objects in a row and ask students to explain how they know the middle one is longer than the first but shorter than the last.
Units that teach this standard
Find where 1.MD.A.1 lands in the program you teach. Each unit has a guide written for families. Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence.
Bridges in Mathematics
enVision Mathematics
Everyday Mathematics
Go Math!
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Reveal Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Ordering three things from shortest to longest for a plain-language look at this skill, with three questions to try together and ideas for helping at home.
Help every student practice measurement and data at home
In Bobby's Math Club, students practice 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 for every family.
See how it works for teachers
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.