A plus sign does not automatically mean “put numbers together,” and a minus sign does not automatically mean “borrow.” Begin by asking what changed. Did two amounts join? Was part removed? Is an unknown amount the distance between two known amounts? The meaning of the situation tells you which operation and which model fit.
MATH-102 · MODULE 02
Addition and Subtraction Methods
Build totals and differences with models, flexible strategies, and visible checking.
A complete learning route
Build a method you can explain, not a string of answers to rush through.
This course begins each module with a teaching conversation, then moves through visible models, worked reasoning, connected practice, and a useful check. Use paper, counters, bottle caps, or a pencil line whenever a model helps.
Restoring this module…
Before you begin
Addition and subtraction describe changes—not columns to copy.
This module makes the two operations visible with number lines, place-value pieces, and part-whole bars. Each representation has a job. A number line shows movement or difference. A bar shows a whole and its parts. Place-value pieces show why regrouping is an exchange of units, not a mysterious rule.
When you practice, pause before writing an equation. Label the starting amount, the change, and the amount you need to find. Then choose a strategy that preserves those meanings. A reliable check rebuilds the original relationship: subtraction can be checked by addition, and addition can be checked by estimating the total.
Start
Name the change before calculating
Learning target
Addition and subtraction describe different changes in a situation.
A total grows when quantities join. A difference describes what remains or how far apart two quantities are.
Read or listen to the teaching conversation for this step
Module 2, Start
Transcript: Before choosing a method, name the change. Does the amount grow, shrink, or show the distance between two amounts?
Guided practice
Work one idea at a time.
Each question comes after a model or explanation. A wrong response opens support and a chance to rebuild the idea; it never counts as complete.
A growing total
A team collected 126 cans on Monday and 89 on Tuesday. Which equation finds the total?
total cans126 Monday89 Tuesday
Server-scored mastery check
Show what you can do without a hint.
The server selects an original equivalent mastery set. A pass needs at least 80% plus evidence on the module’s central ideas.
Complete each guided-practice item correctly to open this mastery check. You have a safe path to every idea; a wrong practice response never closes the route.