Place Value CSI Mystery Worksheets | Grades 2–6 | The Three-Digit Suspect

Place value and ordering 3 digit numbers from least to greatest are the whole job in these fall CSI math worksheets, a CSI Mystery Detective case made for October. The Suspect Number is a mystery with a twist: four digits turned up at the crime scene and nobody knows which number they made, so 3rd grade, 4th grade and 5th grade students build every number those digits allow, line the suspects up from smallest to biggest, and work out which tens and hundreds each sits between until two remain. It is a math review that feels like an investigation, not a drill. Color and black-and-white versions with answer keys, and nothing to prepare beyond printing.

The Case: The Suspect Number

Four digits were found at the crime scene and nobody knows which number they were arranged into. Your students take the investigation through in stages: decode the first message, build every number those digits could make, put the survivors in a police line-up, then research who each one lives nearest to. By the end two numbers are left and one of them is going to break.

What's Inside

• A letter-and-number cipher that decodes the opening message
• Building three-digit numbers from a given set of digits
• Ordering the suspect numbers from smallest to biggest in a line-up
• Working out which tens and hundreds each number sits between
• A final shading puzzle that separates the last two suspects
• 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 an investigation on paper: students do the math, and the math names the answer. Each correct step clears one candidate, and the last one standing closes the case. A CSI Mystery Detective case behaves like a math escape room with the locks taken out - no app, no props, no prep - and it is self-checking in a way math worksheets are not, because a wrong answer leaves more than one possibility alive. Use it as a whole math activity, in math centers, or as detective activities for early finishers.

When to Use This Resource

• The first weeks back at school, to see what came back with them
• Place value and ordering review before or after a unit test
• 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 3rd grade, 4th grade and 5th grade. Third graders usually pair up for the line-up page; fourth and fifth graders run the investigation independently inside a lesson. It also suits 2nd grade students who are secure with three-digit numbers and want something longer.

Why Teachers Love CSI Mystery Detective Cases

• Zero prep - print and hand out
• Self-checking by design, because an early error shows up later
• Place value practice with a reason to be accurate
• Works as a whole lesson, a center, or a filler for an awkward afternoon

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