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"Great resource, low prep, easy to use, and fun! Thank you for sharing this! Highly recommend to other teachers!"

Brandie K.

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"My students loved this resource! They were engaged and were able to complete the tasks with ease."

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"I have enjoyed every purchase I've made from your store. The students are always so engaged!"

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Kiwiland Education

Decimals & Multiplication CSI Mystery Worksheets | Grades 4–6 | Aliens in the Attic

$4.50 USD

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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  • Thank you from Kiwiland Education

"Great resource, low prep, easy to use, and fun! Thank you for sharing this! Highly recommend to other teachers!"

Brandie K.

Verified buyer

"My students loved this resource! They were engaged and were able to complete the tasks with ease."

Gina H.

Verified buyer

"I have enjoyed every purchase I've made from your store. The students are always so engaged!"

Karen C.

Verified buyer

How CSI Math Mysteries Work

CSI Math Mysteries turn regular math practice into a clue-based investigation. Students solve problems, use their answers as evidence, and eliminate suspects until the case is solved.

1

Read the Case

Students begin with a short mystery scenario and find out what needs to be solved.

2

Solve the Clues

Each clue gives students focused math practice using the target skill for that resource.

3

Eliminate Suspects

Students use their answers to remove suspects from the investigation one clue at a time.

4

Crack the Case

By the end, only one suspect remains and students can reveal the answer to the mystery.

No apps, locks, passwords, or student logins are required. Just print and go.

New to the format? Read What Is a Math Mystery? for how they work and how to run one in class.

Why Teachers Use CSI Math Mysteries

CSI Math Mysteries turn skill practice into a clue-based investigation students want to solve. They are easy to prep, flexible for different classroom routines, and help students practice math skills while using logic, reasoning, and careful problem solving.

Teacher-Friendly Review

Practice that feels like a mystery, not another worksheet.

CSI Math Mysteries help students stay focused by turning skill practice into a clue-based case. They are easy to prep, simple to use, and flexible enough for busy classroom routines.

No-Prep and Print-and-Go

Use the pages right away for review, math centers, sub plans, small groups, early finishers, or homeschool math.

Encourages Careful Thinking

Students need accurate answers to eliminate suspects, which encourages checking, reasoning, and attention to detail.

Easy to Fit Into Lessons

Use a full mystery in one session or split the clues across centers, partner work, intervention, or review rotations.

Builds Student Confidence

The mystery format gives students a clear purpose for practicing math skills and helps make review feel more rewarding.

CSI Math Mysteries combine focused math practice with problem solving, logic, and a detective-style task that students can complete independently or with support.

More like this

From CSI Mysteries

See all CSI Mysteries

Frequently Asked Questions For CSI Math Mysteries

Printable CSI Math Mystery worksheets that turn math practice into clue-based detective investigations.

Is this CSI Math Mystery a digital activity?

No. This is a printable PDF resource. Students complete the CSI Math Mystery on paper. No physical item will be shipped.

Do students need apps, locks, passwords, or logins?

No. Students do not need apps, locks, passwords, or logins. Teachers can print the pages and use the CSI Math Mystery straight away.

How do students solve the CSI Math Mystery?

Students solve math clues and use their answers to eliminate suspects. Each correct answer helps them narrow down the case until only one suspect remains.

Can this CSI Math Mystery be used for sub plans?

Yes. CSI Math Mysteries work well for sub plans because students can work through the clues independently, with a partner, or in small groups.

Can this CSI Math Mystery be used for homeschool?

Yes. This printable CSI Math Mystery can be used for homeschool lessons, tutoring, review practice, enrichment, or extra math support.

Will this work for early finishers or math centers?

Yes. CSI Math Mysteries are a good fit for early finishers, math centers, small groups, independent work, review lessons, and extra practice activities.

Aliens in the attic CSI mystery detective decimals grades 4-6

Decimals & Multiplication CSI Mystery Worksheets | Grades 4–6 | Aliens in the Attic

$4.50

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