2-Digit Addition with Regrouping

Inside the case file

After state testing activities, math centers and sub plans for the last weeks: five CSI Mini Mystery Detective math case files on 2 digit addition with regrouping, for 2nd grade and 3rd grade, with a summer theme. Students add on each crime sheet, then cross a suspect off the lineup until one name is left, which turns regrouping practice into math worksheets and math activities that hold up when nothing else does. End of year math for May and June, then early finishers, homework, morning work and back to school review in August. No prep CSI math, with detective activities and full answer keys.

The last weeks of the school year need lessons that run themselves, and these do. Students add, match the total to a suspect, cross the name off and keep going, so a whole class stays busy without you circling the room. One case a day for a week, or all five as a math center, and the answer keys handle the grading.

The Cases

1. The Missing Sun Hat - gone on the hottest day
2. The Lost Towel - left at the pools by somebody
3. Summer Holiday - a surprise trip and no destination
4. Acts of Kindness - good deeds with nobody taking credit
5. Mystery Gift - a gift with nothing written on it

What's Inside

• Five case files, each with a crime sheet and its own lineup of suspects
• Two digit addition with regrouping on every page
• A summer setting throughout: the beach, the pools and the last week of school
• 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 questions on the crime sheet produce those numbers, and a correct answer knocks a suspect out until one name is left holding it. 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. One case fits one class period.

When to Use This Resource

May and June is what this was made for, in those strange weeks after state testing when the math still has to happen and the class has mentally left the building. It keeps carrying practice going in a form students will finish, and it is exactly the right thing to leave in a sub folder at that time of year. A missed carry takes out the wrong suspect, so nobody hands in a page without noticing.

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

Grade Levels

Written for 2nd grade, where two digit regrouping sits in the standards, and used with 3rd graders as an end of year check. First graders take it in the final term once they are adding two digit numbers confidently.

Why Teachers Love These Cases

• Holds attention in the weeks after testing, when nothing else does
• Students catch a missed carry themselves when the wrong name comes off
• No prep at the busiest end of the year
• Works with a whole class, a small group, partners, or one student alone

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