3-Digit Subtraction with Regrouping | Mystery Detective Worksheets | Grades 2–4 | Halloween Zombie Theme

Zombie 3 digit subtraction with regrouping worksheets for 2nd grade and 3rd grade, five Halloween math case files, Mystery Detective style. October math activities for the two weeks before Halloween, then no prep math centers, early finishers, homework, morning work and sub plans, print and go with full answer keys. Find the zombie, the classmate, the principal and the lair by borrowing across the tens and hundreds on every page, where each answer crosses a suspect off the lineup and a wrong one crosses off nobody, so a CSI Mini Mystery Detective marks itself.

Students will happily work through five pages of subtraction to find a zombie, and that is the whole reason this set exists. The story runs across the CSI Mini Mystery Detective math cases so they come back for the next one, and the lineup catches a borrowed ten gone wrong before you do. Pair it with the zombie addition pack for a full Halloween week.

The Cases

1. Find the Zombie - one is hiding in the school
2. Zombie Classmate - one classmate is not human
3. Zombie Principal - the principal has turned
4. Zombie Attack - the whole school is turning
5. Zombie Lair - a hidden lair in the building

What's Inside

• Five case files, each with a crime sheet and its own lineup of suspects
• Three digit subtraction with regrouping on every page
• Borrowing needed across the tens and the hundreds
• 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. The suspects stand in a lineup with a number each, the questions on the crime sheet produce those numbers, and a correct answer knocks a suspect out until the last name standing is the culprit. There is nothing to cut or set up, so the arithmetic carries the whole thing, which is what separates detective activities from ordinary math worksheets.

When to Use This Resource

October is the month, but the real reason to use this is that borrowing twice in a sum needs far more practice than a unit usually allows, and five zombie cases will get that practice done. The story pulls students through page after page of the skill they would otherwise stall on. A wrong borrow crosses off the wrong suspect, so the mistake is caught before it becomes a habit across the whole sheet.

It covers 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 2nd grade and 3rd grade, where three digit subtraction with regrouping sits in the standards. Fourth graders take it as an October refresher, and second graders manage it once two digit borrowing is secure.

Why Teachers Love These Cases

• Borrowing across two columns, which is the part that needs the repetitions
• Students catch a wrong borrow when the wrong suspect comes off
• No prep, and the answer keys make grading quick
• Works with a whole class, a small group, partners, or one student alone

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