4-Digit Subtraction with Regrouping | Mystery Detective Worksheets | Grades 3–5 | Valentine's Day

4 digit subtraction with regrouping worksheets for 3rd grade and 4th grade, five Valentines Day math activities as Mystery Detective cases, borrowing across four columns throughout. No prep February math activities with full answer keys, print and go, for early finishers, math centers, homework, morning work and sub plans. Flowers left overnight, a card with no signature and a bouquet with the label torn off carry the week, and every answer matches one suspect only and crosses them off the lineup, and a CSI Mini Mystery Detective gets four digit borrowing done in the week nobody wants to do it.

Four digit subtraction is the biggest borrowing a third grader meets, and a valentine to trace is what gets five CSI Mini Mystery Detective math cases done in the second half of February. The lineup does the checking, so the marking is student-led and a glance at the key is all you need.

The Cases

1. Bunch of Flowers - left on the teacher's desk overnight
2. Valentines Day Card - a card with no signature
3. Valentines Day Flowers - left for the teacher overnight
4. Love Songs - somebody is singing love songs
5. Mystery Bouquet - flowers with the label torn off

What's Inside

• Five case files, each with a crime sheet and its own lineup of suspects
• Four digit subtraction with regrouping on every page
• Borrowing across four columns, which is the hardest subtraction at this level
• 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 a single page case your class cracks with math. The suspects stand in a lineup with a number each, the crime sheet produces those numbers, and a correct answer knocks one suspect out until the last name standing is the culprit. There is no kit and nothing to assemble, so what carries it is the arithmetic, which is what makes detective activities land where math worksheets slide off. One case runs a class period.

When to Use This Resource

Four digit borrowing needs far more repetitions than the unit allows, and these five cases supply them in a form third and fourth graders will finish. February gives you a reason to hand it out, and it still works in April when you want the columns automatic before decimals arrive. One wrong borrow names the wrong suspect, so students trace the error back themselves.

It suits test prep, homework, math centers, morning work, early finishers, sub plans, homeschool lessons and spiral review, with a class, a small group or one student.

Grade Levels

Written for 3rd grade and 4th grade, where four digit subtraction sits in the standards. Fifth graders use it as a fluency refresher, and second graders take it once three digit borrowing is secure.

Why Teachers Love These Cases

• Five full pages on the hardest subtraction third graders meet
• Students trace a wrong borrow back when the wrong name 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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