Addition & Subtraction CSI Mystery Worksheets

Inside the case file

Haunted Halloween CSI math worksheets for 2nd grade and 3rd grade: 2 digit addition and subtraction with regrouping, ready for October. Inside the CSI Mystery Detective case, the candy the teacher promised the whole class has vanished from the desk - not eaten, gone, with a cold draft down the hallway nobody can explain. The mystery is which ghost took it. Each correct answer rules one ghost out of the line-up, so students keep working because they want the name. Color and black-and-white versions, answer keys, nothing to cut. They check worked answers for errors, read a map key, and follow a subtraction path where the running total settles the clue.

The Case: Haunted Halloween

Halloween is finally here and your teacher has promised sweets for the whole class. Everybody is in a good mood, nobody is working, and then the sweets are gone. Not eaten - gone, along with a cold draught down the corridor that nobody can explain. There is a ghost in this school, and your students have to work out exactly which one.

What's Inside

• Checking worked answers for errors and tallying which are correct
• Reading letters off a map with a key to decode a clue
• Multi-step problems where the last answers unlock a code chart
• Subtraction along a path where the running total settles the clue
• Subtraction problems used to color the correct arrow forward
• Full color and black-and-white versions of every page
• Answer keys for the whole case

What Is a CSI Mystery Detective Case?

In a CSI Mystery Detective case, the suspect list does the job an answer key usually does. Students solve, each correct answer clears one name, and the last one standing is the culprit. It is a math escape room made of paper - no locks, no app, nothing to cut or set up. That is also what makes it self-checking where ordinary math worksheets are not: bad arithmetic leaves a description that fits nobody. It runs as a whole math activity, in math centers, or as detective activities for early finishers.

When to Use This Resource

• Halloween week in October, when a normal worksheet will not hold them
• The days before a holiday, when you still want real math done
• Math centers, early finishers and independent work
• Emergency sub plans that run themselves
• End of year review, when attention is thin and the work still has to happen

Grade Levels

Built for 2nd grade and 3rd grade. Second graders usually run it comfortably; third graders finish inside a lesson and often ask for another. It also suits 4th grade students who need 2 digit addition and subtraction review in a form that does not feel 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 Halloween activity that still does real math
• Works as a whole lesson, a center, or a filler for an awkward afternoon

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