3-Digit Addition with Regrouping

Inside the case file

Christmas Around the World 3 digit addition math worksheets for 2nd grade and 3rd grade: five Mystery Detective style math cases with regrouping on every page. December math activities, no prep, print and go with full answer keys, for math centers, early finishers, homework, morning work and sub plans. Santa has lost every label, and the story runs across all five pages, so a class comes back for the next one. It is 3 digit addition with regrouping practice for 2nd grade and 3rd grade that pairs with a Christmas Around the World unit, works as December math activities for math centers or morning work, and every CSI Mini Mystery Detective page is self-marking.

One story across five CSI Mini Mystery Detective math cases is why this set holds a class for a week rather than a lesson, and it pairs with a Christmas Around the World unit without any extra planning. Students add their way to each label, and the marking is student-led, with answer keys included.

The Cases

1. Christmas Present One - Santa has lost every label
2. Christmas Present Two - a second gift with no name
3. Christmas Present Three - one more parcel nobody can claim
4. Christmas Present Four - another gift Santa cannot deliver
5. Christmas Present Five - the last parcel with no name

What's Inside

• Five case files, each with a crime sheet and its own lineup of suspects
• Three digit addition with regrouping on every page
• One running story across all five cases, with a present to deliver in each
• Each answer matches one suspect and no other, so the page checks itself
• A full answer key for every case
• Print and go: no cutting, no laminating, nothing to prepare

What Is a CSI Mini Mystery Detective?

A CSI Mini Mystery Detective is one printed page carrying one crime and one lineup. Each suspect has a number, the crime sheet produces those numbers, and a correct answer removes that suspect until a single name is left. Nothing is laminated, charged or bought, so the math does the whole job, and that is the difference between these detective activities and a page of math worksheets. A case runs about a class period.

When to Use This Resource

December is the month, and the Christmas Around the World unit is the natural place for it, but what makes this one work is the story running through all five cases. Students finish one present and want the next, which is how you get five pages of carrying practice out of a class that has stopped listening. A dropped carry sends the wrong gift to the wrong person and they spot it.

Use it for test prep, homework, math centers, morning work, early finishers, sub plans and homeschool lessons, with a whole class, a small group or one child alone.

Grade Levels

Written for 2nd grade and 3rd grade, where three digit addition with regrouping sits in the standards. Fourth graders take it as a December refresher, and second graders manage it once two digit carrying is secure.

Why Teachers Love These Cases

• One story across five cases, so students want the next page
• Students see a dropped carry when the wrong name comes off the lineup
• No prep in the last weeks of term
• Works with a whole class, a small group, partners, or one student alone

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