3-Digit Addition & Subtraction Regrouping

Inside the case file

Thanksgiving 3 digit addition and subtraction with regrouping for 2nd and 3rd grade, in ten CSI Mini Mystery Detective math cases. Every page mixes addition with regrouping and three digit subtraction with regrouping, including subtracting across zeros. Use the cases in your November math centers, for morning work or as homework. There's nothing to prep, and every case has an answer key.

The parade turkey has escaped, somebody stuffed corn husks into the sousaphone, and the roast turkey has vanished from the counter. Your students are the detectives on every case. Each 3 digit addition and subtraction problem they get right crosses another suspect off the list. It's self-checking, too. When only one name is left, they've got the whole page right, and that last suspect is the villain.

What Is a CSI Mini Mystery Detective?

A CSI Mini Mystery Detective is a full detective case printed on a single page. There's a short story at the top, a set of problems, and a lineup of suspects with a number beside each one. Nothing needs cutting out or laminating. Students only need a pencil.

What's Inside

• 160 problems across 10 one-page Thanksgiving cases, 16 on each page
• Answer keys for all ten cases
• Eight additions and eight subtractions on every page. Sums stay at 999 or less, and every subtraction answer has three digits
• Regrouping in the ones, in the tens or in both, plus two subtractions across a zero on each page
• A How to Regroup page in hundreds, tens and ones, with 368 + 475 and 532 - 278 worked out
• Teacher instructions, a contents page, a Detective's Case Log and a Top Detective certificate
• 30 pages, all black and white for easy printing

The Cases

1. The Gobbler on the Loose - the turkey out of its pen before the parade
2. The Missing Marching Drum - the band's big drum gone on Thanksgiving morning
3. The Stuffed-Up Sousaphone - corn husks pushed into the sousaphone
4. The Runaway Hay Wagon - the hayride wagon rolling down the hill with nobody on it
5. The Swapped Giant Pumpkin - a giant pumpkin traded for a tiny one overnight
6. The Missing Scarecrow Hat - the scarecrow's floppy hat taken
7. The Empty Apple Bushel - a bushel of apples gone from the farm stand
8. The Lost Football Trophy - the trophy missing before the big game
9. The Scattered Leaf Pile - Grandpa's leaf pile kicked all over the yard
10. The Stolen Feast Turkey - the roast turkey gone from the counter

When to Use This Resource

Bring the cases out in the two weeks before Thanksgiving, once your class has learned to regroup with three digit numbers. Addition and subtraction are on the same page, so students have to read each sign before they start. The How to Regroup page can sit beside an intervention group as a reminder of the steps. A single case works as a bell ringer or a review before a test, and a few can go in your sub plans for the days before the break. Homeschool families can use the pack too, and 4th grade teachers can use it to review regrouping.

Grade Levels

Written for 2nd grade (2.NBT.B.7) and 3rd grade (3.NBT.A.2), where students learn to add and subtract within 1,000. In 4th grade it's a regrouping review.

Why Teachers Love Mystery Detectives

All Mystery Detective packs follow one routine. After the first case, students can start any other case on their own, in this pack or a different one. The cases don't build on each other. Pick whichever one fits your week. Naming the villain gives students a clear finish line, and you can check a page against its key in a minute or two.

Want more cases like these?

Follow Kiwiland Education to discover more CSI Mini Mystery Detective cases, no-prep math activities, and detective-themed printables for elementary classrooms.

https://www.teacherspayteachers.com/Sellers-Im-Following/Add/Kiwiland

Get it on TPT ↗