Addition, Subtraction & Times Tables CSI Mystery

Inside the case file

Addition and subtraction with regrouping within 100 power these alien CSI math worksheets, a CSI Mystery Detective case for 2nd grade and 3rd grade. Subtraction with regrouping gets the heaviest practice, plus a few early multiplication facts. Use it in April, when 3rd grade math needs a fresh reason to be careful. The new teacher at the front of the room has too many eyes, and the math on the board is the only evidence. Nothing to cut or set up, just print in color or black and white. Students decode a space map and follow a planet trail, ruling out a suspect with every correct answer, and answer keys cover the whole mystery.

The Case: Meet My Alien Teacher

It is the first day of a new school year, and you have spent the whole summer wondering who you are going to get. You bolt your breakfast, get to class early, and there is something not quite right about the person standing at the front. The skin. The number of eyes, if you count properly. Your students have one morning to work out exactly what their new teacher is, and the only evidence is the math left on the board.

What's Inside

• Using a key to decode a secret message from letters on a space map
• Addition and subtraction within 100, checked for errors against a tally
• Multiplication used to color the correct star and arrow to the next clue
• Addition along a planet trail where the running total settles the clue
• A letter grid circled by multiplication answers, then unscrambled
• Full color and black-and-white versions of every page
• Answer keys for the whole case

What Is a CSI Mystery Detective Case?

Give a class a crime, a suspect list and a page of math worksheets and you have a CSI Mystery Detective case. The answers do the work: each correct one removes a name until only the culprit remains. It is a math escape room in everything but the hardware - no locks, no app, no prep. Detective activities also carry their own marking, because a wrong answer stops the case closing at all. Run it as a full math activity, drop it into math centers, or keep it for a sub plan.

When to Use This Resource

• The first weeks back at school, when you want the math to feel like fun
• Regrouping review before or after a unit test
• Math centers, early finishers and independent work
• Emergency sub plans that run themselves
• Whole-class detective sessions, small groups or partner work

Grade Levels

Built for 2nd grade and 3rd grade. Second graders usually work the regrouping pages in pairs; third graders can run the case independently. It also suits 4th grade students who need addition and subtraction review in a form that does not look like going back a year.

Why Teachers Love CSI Mystery Detective Cases

• Zero prep - print and hand out
• Self-checking by design, because a wrong answer breaks the deduction
• A back-to-school activity that still does real math
• Works as a whole lesson, a center, or a filler for an awkward afternoon

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