4-Digit Addition with Regrouping | Mystery Detective Worksheets | Grades 2–5 | Winter Theme

Winter snow day 4 digit addition with regrouping math activities for 3rd grade and 4th grade: five math cases, each a Mystery Detective page with carrying across four columns. January and February math worksheets with full answer keys, no prep, print and go, for math centers, early finishers, homework, morning work and sub plans. A snowman built overnight, an empty seat and a surprise ski trip carry the cases, every total matches one suspect only and crosses them off the lineup, and a CSI Mini Mystery Detective is the page a class will finish in the dead of winter.

The long stretch after the holidays is when a lesson needs to run itself, and four digit addition with a culprit at the end of it does. Students add, find the suspect with that total and cross the name off, so every page is self-marking, and one CSI Mini Mystery Detective math case a day carries the class through a slow January week.

The Cases

1. Surprise Snowman - built overnight by somebody
2. Winter Blues - one seat is empty today
3. Skiing and Snowboarding - somebody is off on a surprise trip
4. Mittens and Gloves - one mitten short on a cold day
5. Toboggan Turn - who gets the next run

What's Inside

• Five case files, each with a crime sheet and its own lineup of suspects
• Four digit addition with regrouping on every page
• Carrying across four columns, so students cannot rely on three digit habits
• 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 page, one crime and one class period. Each suspect in the lineup is tagged with a number, the questions produce those numbers, and a correct answer knocks a suspect out until the last one standing is the culprit. Nothing needs cutting, laminating or charging, which is why these detective activities get handed out on days that would otherwise call for math worksheets.

When to Use This Resource

January and February is the stretch this was written for, when the class is back from the break and three digit addition needs pushing on to four. The extra column catches students who have been adding on autopilot, and five cases give you enough practice for the habit to change. A carry missed in the thousands names the wrong suspect, so they go back over the whole sum.

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

Grade Levels

Written for 3rd grade and 4th grade, where four digit addition sits in the standards. Fifth graders take it as a fluency check, and second graders manage it once three digit carrying is secure.

Why Teachers Love These Cases

• Four columns, which catches students adding on autopilot
• Students recheck the whole sum when the wrong suspect comes off
• No prep in the long stretch after the holidays
• Works with a whole class, a small group, partners, or one student alone

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