Add Hundreds with an Exchange
Align the supplied place values and add from ones upward.
About 20 minutes, plus any extended practice
Open lesson 1Explain Regrouping and Two-Step Stories
Regroup in addition and subtraction, adjust mental sums, and keep two story changes separate.
Before you begin
- Add and subtract two-digit amounts with drawings.
Choose by skill rather than age alone. Read with an adult when useful, revisit a lesson, or explore another grade.
Follow the lesson sequence
Rename a Ten Before Subtracting Ones
Read the needed ones subtraction.
About 20 minutes, plus any extended practice
Open lesson 2Adjust a Mental Sum Around a Friendly Ten
Replace the near-ten addend with the next multiple of ten.
About 15 minutes, plus any extended practice
Open lesson 3Track Two Different Changes in a Story
Write the starting amount, add or subtract the first change, then use that result for the second change.
About 20 minutes, plus any extended practice
Open lesson 4Review and transfer
After the lessons, try 4 new review cases and a practical task. Each answer has an explanation and a link back to the related lesson.
Open the unit reviewGuest answers are temporary. Keep your own paper or document; this unit does not certify completion or record a school grade.
Topic references
- Common Core State Standards, mathematics: 2.NBT.B.5 — Regroup in addition and subtraction, adjust mental sums, and keep two story changes separate.
- Common Core State Standards, mathematics: 2.NBT.B.7 — Regroup in addition and subtraction, adjust mental sums, and keep two story changes separate.
- Common Core State Standards, mathematics: 2.NBT.B.9 — Regroup in addition and subtraction, adjust mental sums, and keep two story changes separate.
These references informed the topic selection. They do not certify complete standards alignment.