Montana Math MT.PLUS.ALG.MOD.4

MathGrades 9–12Modeling

The Standard

Choose a level of accuracy appropriate to limitations on measurement when reporting quantities in modeling situations.

2026 Montana Mathematics Content Standards · Algebraic and Functional Reasoning

Teacher's field guide

What Students Need to Do: Students use measurements in a calculation and decide how precisely to report the result. They explain why calculator digits do not make a measured quantity more accurate.
What Mastery Looks Like: Given a tabletop measured as 1.24 m by 0.63 m, a student calculates 0.7812 m² and reports about 0.78 m². They include units and explain why the measurements do not support reporting all four decimal places.
Common Misconceptions: Students often copy every digit from the calculator. Some round each measurement before calculating, which can change the result. Others assume every answer must have the same number of decimal places as the measurements.
How to Assess It: Ask: “A shelf measures 1.24 m by 0.63 m. Your calculator shows 0.7812 m². What area would you report, and why?”

Lesson moves

Give pairs rulers to measure a desktop to the nearest centimeter, calculate its area, and label a sensible rounded result.
Display 1.24 m × 0.63 m and ask, “Should we report 0.7812 m² or about 0.78 m²? Why?”
Have pairs match measurement cards to rounded area cards, then explain one match to another pair.
Measure a classroom wall to the nearest tenth meter, check a paint can’s coverage label, and estimate whole cans to buy.

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