2.9.B
The Standard
describe the inverse relationship between the size of the unit and the number of units needed to equal the length of an object
Texas Essential Knowledge and Skills for Mathematics
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students measure one object using units of different sizes. They explain why smaller units require a greater count, while larger units require a smaller count.
What Mastery Looks Like
- A student measures the same object with two unit sizes and records both results accurately. The student explains that smaller units produce a greater count and larger units produce a smaller count.
Common Misconceptions
- Students may think a larger unit gives a larger measurement number. They may also leave gaps, overlap units, or mix unit sizes while measuring.
How to Assess It
- Give students a pencil and both inch tiles and paper clips. Ask them to measure with each, then write why the two numbers differ.
Lesson moves
Ways to Teach It
Measure a desk with linking cubes and craft sticks, then compare the counts and explain why they differ.
Ask, “Would you need more footsteps or more baby steps to cross the room?” Have students explain in words or pictures.
Play Unit Match by pairing object cards with predicted measurements using large tiles and small tiles, then check with actual materials.
Compare measuring a hallway with student steps and teacher steps, then discuss why builders use agreed measurement units.
Keep exploring
Related Standards
- 2.9.A
find the length of objects using concrete models for standard units of length
- 1.7.D
describe a length to the nearest whole unit using a number and a unit
- 1.7.B
illustrate that the length of an object is the number of same-size units of length that, when laid end-to-end with no gaps or overlaps, reach from one end of th...
- 1.7.C
measure the same object/distance with units of two different lengths and describe how and why the measurements differ
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