Decimals & Multiplication CSI Mystery Worksheets

Inside the case file

CSI Mystery Detective decimals work for 5th grade and 6th grade: adding, subtracting and multiplying decimals, and comparing which is greater, on one set of CSI math worksheets. It covers adding and subtracting decimals, then pushes into multiplying decimals with large answers, a strong March activity ahead of testing season. Something has lived in the attic a while, and its decimals are the only clue to how many eyes and arms it has. Color and black-and-white pages are both included, so it goes straight from printer to desk. Students compare, add along a path and color a multiplication trail, crossing off a suspect per correct answer, with answer keys to close the mystery.

The Case: Aliens in the Attic

One stormy night you go to bed early with a book, listening to the rain lashing the window and the trees thrashing in the wind. Then, over the top of the storm, something moves in the attic. It is not the wind, and it is not the house settling. Whatever is up there has been there a while, and the only way to work out what it is - and how many eyes and arms it has - is to solve the decimals it left behind.

What's Inside

• Comparing decimals to decide which is greater and which is lesser
• Adding decimals along a path where the running total settles the clue
• Multiplying decimals, including problems with large answers
• Subtracting decimals to check a suspect off the line-up
• A color-the-arrow trail that only works if the multiplication is right
• Full color and black-and-white versions of every page
• Answer keys for the whole case

What Is a CSI Mystery Detective Case?

A CSI Mystery Detective case turns a page of math into evidence. Students solve, each correct answer strikes one name off the suspect list, and the case closes on the last one standing. There is nothing to unlock, download or prepare - it is a math escape room made of paper. Detective activities also police themselves in a way ordinary math worksheets cannot: an error leaves a culprit nobody can arrest, so the class goes back over it. A math activity that carries a lesson, a center rotation, or a sub plan.

When to Use This Resource

• Decimal 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
• Whole-class detective sessions, small groups or partner work

Grade Levels

Built for 5th grade, and it carries comfortably into 6th grade. Fourth graders who have met decimals can manage it with support, usually working in pairs on the multiplication pages. It also gives older students who need decimal review something to work on that does not look like remedial work.

Why Teachers Love CSI Mystery Detective Cases

• Zero prep - print and hand out
• Self-checking by design, because a wrong answer breaks the deduction
• Decimal practice students will actually finish
• Works as a whole lesson, a center, or a filler for an awkward afternoon

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