Addition & Subtraction CSI Mystery Worksheets | Grades 2–5 | The Missing Stationery

August and September back to school CSI math worksheets: addition and subtraction with two-digit and three-digit numbers, some early multiplication, and a CSI Mystery Detective story to carry it. On the first morning back, 2nd grade and 3rd grade students find every pencil and crayon gone, and whoever cleared the room left footprints and enough math behind to be named. It is back to school math with a purpose, and the mystery gives a new class a shared job while you learn their names. Print and go, nothing to prepare. Students add along a crayon trail, decode sums with a letter key and color the right arrow forward, losing a suspect each time. Answer keys included.

The Case: The Missing Stationery

There has been an emergency at school. Your students walk into class on the first morning back and every last piece of stationery is gone - pencils, crayons, scissors, the lot. Somebody came in over the holidays while the building was empty and cleared the room out. They left footprints, though, and enough math behind to say exactly who they were.

What's Inside

• Addition along a crayon trail where the running total settles the clue
• Checking worked answers for errors and tallying which are correct
• Three-digit addition decoded through a letter key
• Multiplication used to color the correct circle and arrow forward
• A matching page where the line drawn passes through the letter that matters
• Full color and black-and-white versions of every page
• Answer keys for the whole case

What Is a CSI Mystery Detective Case?

It is a printable CSI Mystery Detective case: a back to school escape room on paper, with no locks, no apps and nothing to set up. Students work a page of back to school math worksheets, and every answer they get right crosses another suspect off the line-up until one name is left. Detective activities like this one run themselves, because a careless answer sends the description the wrong way and students go back over their own work.

When to Use This Resource

• The first days back at school, when you want the math to feel like fun
• Seeing what came back with them after the summer
• 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 work the three-digit addition in pairs; third graders can run the case independently inside a lesson. It also suits 4th grade students who need 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 first-week activity that still does real math
• Works as a whole lesson, a center, or a filler for an awkward afternoon

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