Length as Sum of Parts with Unit Matching
A total length or distance is the sum of its segments, but only after every measurement is expressed in the same unit. Learners unify handspans and rulers, convert km/m/cm, and accumulate multi-leg distances. Matching units before combining is the habit that prevents the most common measurement errors.
grade 2–4 MD Analyze the UnitsIdentify Subproblems
Progression (7)
2-2 1. Find one handspan from measured counts 2.MD.A.12.MD.B.5
2-2 2. Smaller unit, more measured counts 2.MD.A.1
2-2 3. Convert to one unit, then compare lengths 2.MD.A.14.MD.A.1
3-1 4. Sum distances and times across legs 4.MD.A.24.MD.A.13.MD.A.1
3-1 5. Match units before comparing path lengths 4.MD.A.14.MD.A.22.MD.A.4
3-1 6. Total length is the sum of its parts 4.MD.A.14.MD.A.22.MD.B.5
4-1 7. Bigger units express numbers more simply 4.MD.A.14.MD.A.2