LESSON PLAN

Addition and Subtraction to 10,000

Apothem Team

Grade 4 · Computational Fluency

LESSON AT A GLANCE

Warm-up

5 min

Explore

15 min

Consolidate

10 min

Practice

12 min

Exit ticket

3 min

Warm-up

Number talk: 3,994 + 2,008. Students solve mentally. Strategies: 4,000 + 2,000 = 6,000, subtract 6 = 5,994, then add 8 = 6,002. Or decompose: 3000+2000=5000, 900+0=900, 90+0=90, 4+8=12. 5000+900+90+12=6002. Compare strategies.

Explore

Fish stock scenario: a lake has 7,340 rainbow trout. 1,852 are caught in spring and 2,106 in fall. How many remain? Students solve with two strategies each, show an estimate, and verify with the inverse. Discuss: which strategy was most efficient?

Consolidate

Practice

Students solve 6 four-digit computation problems using at least two strategies each, recording estimates. Exit ticket: estimate then compute 4,892 + 3,641.

Exit ticket

Students solve 6 four-digit computation problems using at least two strategies each, recording estimates. Exit ticket: estimate then compute 4,892 + 3,641.

TIP Estimation must come before computation for four-digit numbers. A student who estimates 4,000+3,000 before computing 3,994+2,896 has a target (close to 7,000) and will catch the error if they compute 5,890.

WORKED EXAMPLES

Solve 8,004 - 2,997 using compensation.

2,997 is close to 3,000. 8,004 - 3,000 = 5,004. Added 3 too many, so add 3 back: 5,004 + 3 = 5,007.

A field trip costs

3,875. Fundraising raised

2,490. How much more is needed?

3,875 - 2,490. Estimate: 4,000 - 2,500 = 1,500. Compute: 3,875 - 2,490 = 1,385. Check: 2,490 + 1,385 = 3,875. Yes.

MATERIALS

•Open number lines

•Base-ten blocks

•Number talk display

•Estimation recording sheets

WATCH FOR

!Subtracting from zero across multiple positions (e.g., 8,004 - 2,997) is the most error-prone case. Compensation converts it to a trivial problem.

!Students may estimate after computing (to validate) rather than before (to predict). The predictive habit is more powerful.