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

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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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Kiwiland Education

Halloween Addition & Subtraction Within 100 CSI Math Mystery Worksheets | Grades 1–3 | The Haunted House

$4.50 USD

Something is haunting the old house on the hill, and only your students' addition and subtraction skills can reveal who. This printable Halloween Addition & Subtraction Within 100 CSI Math Mystery is designed for Grades 1–3 classroom teachers, homeschool parents, and tutors who want focused math practice wrapped in a story students actually care about solving.

Students work through a series of clue pages, use their answers to eliminate suspects, and race to crack the case — all while getting meaningful practice adding and subtracting within 100. No apps, no prep, no fuss.

Quick Details

Grade Levels: Grades 1–3 (mostly used with 3rd — also suits advanced 1st graders or older students needing reinforcement)
Format: Printable PDF
Resource Type: CSI Math Mystery worksheets
Math Skills: Subtraction within 20, adding 1-digit to 2-digit numbers with regrouping, 2-digit addition, greater than / less than, and addition within 100
Pages: 15 pages including answer key
Standards: Supports CCSS 2.NBT.A.4, 2.NBT.B.5, and 2.NBT.B.6
Best For: Halloween and October math, centers, sub plans, early finishers, review, and homeschool
Tech Needed: None — no apps, locks, passwords, or student logins required

Case Summary

The old house at the end of the street has come alive for Halloween — doors slam, lights flicker, and something is clearly hiding inside. Your students are the detectives sent to find out exactly who, or what, is haunting the place.

Each clue page puts addition and subtraction within 100 to work: students subtract within 20, add 1-digit numbers to 2-digit numbers with regrouping, compare numbers with greater-than and less-than, and add within 100 using mental strategies. Every correct answer crosses another suspect off the list.

Because the suspect list is built into the math, students self-check as they go — a wrong answer points to the wrong culprit, so accuracy matters from the first creak to the last. It's spooky-season practice that keeps even your youngest detectives glued to the page.

Can your class work the numbers and unmask whoever is haunting the house? Print the case file and let the investigation begin.

Skills Covered

Students will practice:

  • Subtraction within 20 using mental strategies
  • Adding a 1-digit number to a 2-digit number with regrouping
  • 2-digit addition
  • Greater than and less than
  • Addition within 100
  • Using answers to eliminate suspects
  • Logic, reasoning, and problem solving

What's Included

  • CSI-style Halloween math mystery activity
  • Addition and subtraction clue pages
  • Greater than / less than activity
  • Suspect elimination activity
  • Answer key
  • Print-and-go PDF format

Best Used For

This printable CSI Math Mystery works well for:

  • Halloween and October math activities
  • Math centers and early finishers
  • Substitute teacher plans
  • Small groups and independent work
  • Homeschool math
  • Addition and subtraction review within 100

All of our products are digital downloads — no physical items will be shipped.

  • After purchase, you’ll receive an email with a download link within minutes.
  • Make sure to check your spam or promotions folder if you don't see it right away.
  • If you experience any issues accessing your files, please contact us and we’ll help you promptly.

Due to the nature of digital products, all sales are final.

We do not offer refunds or exchanges once a file has been downloaded.

However, if you encounter any problems with your download or the product itself, please reach out — we're happy to assist.

  • 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.

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.

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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.

Halloween addition and subtraction within 100 CSI Math Mystery cover - The Haunted House, Grades 1-3

Halloween Addition & Subtraction Within 100 CSI Math Mystery Worksheets | Grades 1–3 | The Haunted House

$4.50

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