3-Digit Subtraction with Regrouping

Inside the case file

3 digit subtraction with regrouping Valentines Day math worksheets for 2nd grade and 3rd grade, five Mystery Detective style math cases for the February week. No prep math activities with full answer keys, print and go, for math centers, early finishers, homework, morning work and sub plans. A chocolate surprise with no note, a card on a friend's desk and a voice nobody can place carry the week, the right answer clears a suspect and a wrong one clears nobody, so the borrowing across the tens and hundreds checks itself on every CSI Mini Mystery Detective page.

The week of the class party is when a lesson has to hold itself together, and a CSI Mini Mystery Detective math case holds a second grade class better than a page of subtraction does. Students borrow, match the answer to a name and cross it off, so the marking is student-led and a substitute has nothing to explain.

The Cases

1. Chocolate Surprise - a box appears with no note
2. Friends Valentines Card - a card lands on a friend's desk
3. Acts of Kindness - good deeds with nobody taking credit
4. Singing Love Songs - a voice nobody can place
5. Bouquet of Flowers - flowers with no card attached

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 across the tens and the hundreds, so it is genuine practice
• 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 investigation solved with arithmetic. Each suspect in the lineup carries a number, the crime sheet produces those numbers, and a correct answer takes that suspect out until one name is left. No locks, no app, nothing to assemble, which is why these detective activities get used on days that would otherwise call for math worksheets. Each case fits a class period and works in a center or a sub folder.

When to Use This Resource

The week of Valentines Day is where this earns its money, because you still have subtraction to cover and the class has cards on the brain. Underneath the theme it is straight three digit borrowing, the skill that slips faster than anything else at this level. The wrong difference names the wrong suspect, so students check the column rather than handing the page in and waiting to be told.

It suits 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 a February refresher, and second graders manage it once two digit borrowing is secure.

Why Teachers Love These Cases

• Straight borrowing practice with a seasonal cover on it
• Students check their own columns when the wrong suspect comes off
• No prep in a week with a party in it
• Works with a whole class, a small group, partners, or one student alone

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