Winter Addition & Subtraction CSI Mystery

Inside the case file

Winter math activities for January: addition and subtraction with 2-digit and 3-digit numbers, run as a snow day CSI Mystery Detective case. A snowman appears overnight that nobody remembers building, and 2nd grade, 3rd grade, 4th grade and 5th grade students work out whose it is. Winter CSI math worksheets that play like a game hold attention far better than drill, and this mystery keeps them adding and subtracting to the last clue. Print the pages and they are ready. Students follow an addition path one step at a time, decode answers into a word with a letter key, and spot errors in worked equations before checking the suspect chart. Answer keys included.

The Case: Who Built the Snowman?

You wake to a freezing morning and a thick blanket of snow across the yard. School is called off, everyone is out building - and by the time the street wakes up properly, one snowman is standing where nobody remembers building one. Your class takes the case and works the clues until only one builder is left.

What's Inside

• Addition with 2-digit and 3-digit numbers
• Subtraction to narrow down the final clue
• Following an addition path from start to finish, one step at a time
• Using a key to turn answers into letters and letters into a word
• Deciding whether a worked equation is right or wrong - error spotting, not just answering
• Reading a suspect chart and matching your answers against it
• Answer keys included

What Is a CSI Mystery Detective Case?

A CSI Mystery Detective case is a whodunit whose only clues are answers. Work the page, cross a suspect off with each correct one, and close the case on the name that survives. It runs like a math escape room that needs a printer instead of locks, an app or any setup. Ordinary math worksheets can be half-done and still look finished; detective activities cannot, because a wrong answer leaves nobody matching the description. A math activity for a lesson, for math centers, or for a sub plan.

When to Use This Resource

• Winter and holiday math centers
• The last weeks of term before the December break
• January, when the class comes back and needs something that holds them
• Snow days and shortened timetables
• December, January and February math review
• Sub plans and emergency cover
• Early finishers, morning work and homework

Grade Levels

Designed for 2nd grade, 3rd grade, 4th grade and 5th grade. The 2-digit pages give a 2nd grader a way in, and the 3-digit work keeps a 5th grader who still needs regrouping practice honestly busy rather than bored.

Why Teachers Love CSI Mystery Detective Cases

• No prep at all - print it and hand it out
• Self-checking, so you are not hunting through thirty pages for one slipped digit
• The suspect chart gives every student a reason to go back and check their own working
• Every clue uses a different puzzle shape, so the pack holds attention to the last page
• Quiet, focused engagement on the kind of day when nothing else lands

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