3-Digit Subtraction with Regrouping

Inside the case file

3 digit subtraction with regrouping St Patricks Day math worksheets for 2nd grade and 3rd grade, five Mystery Detective math cases for the March week. No prep math activities with full answer keys, print and go, for math centers, early finishers, homework, morning work and sub plans. Missing green balloons, an invitation with no sender and a shamrock left overnight carry the cases, the right answer clears a suspect and a wrong one lands on nobody, so the borrowing across the tens and hundreds checks itself on every CSI Mini Mystery Detective page.

The day before a St Patricks Day assembly is where these CSI Mini Mystery Detective math cases save you, because a class will subtract its way to the culprit without anyone at the front. Marking is student-led, with the answer keys there for a quick glance.

The Cases

1. Missing Green Balloons - every green balloon disappears
2. St Patricks Invitation - an invitation with no sender
3. Shamrock For Teacher - a shamrock left overnight
4. Leprechaun Dress Up - one teacher is under the hat
5. St Patricks Kindness - somebody is doing good all day

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, not just once per problem
• 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 printable case with a lineup of suspects, each carrying a number. The questions on the crime sheet produce those numbers, a correct answer strikes one suspect off, and the last name standing is the culprit. The elimination only works when the math is right, which is what makes these detective activities show up mistakes a page of math worksheets would hide. One case fits one class period.

When to Use This Resource

March is the obvious month, and the day before a St Patricks Day assembly is the moment this saves you. Underneath the shamrocks it is straight three digit borrowing practice, which is the skill second and third graders lose fastest. Getting a borrow wrong puts the wrong name in the frame, so students check the column themselves and you are not the one finding every mistake.

It covers test prep, homework, math centers, morning work, early finishers, sub plans and homeschool lessons, with a class, a small group or one child 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 March refresher, and second graders manage it once two digit borrowing is secure.

Why Teachers Love These Cases

• Real borrowing practice under a seasonal cover
• Students find the wrong column themselves when the wrong suspect comes off
• No prep in a week full of assemblies and green hats
• Works with a whole class, a small group, partners, or one student alone

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