3rd Grade Math Review CSI Mystery Worksheets
Grades 3–4 · The Missing School Pet
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Inside the case file
3rd grade CSI Mystery Detective activities, 3 digit addition and subtraction with regrouping, multiplication and division facts within 100, rounding to the nearest 10 and 100, and multiplying by multiples of 10 are all included in this printable CSI Mystery Detective for grade 3 classrooms, homeschool families and tutors. It is built for back-to-school review, spiral review, end-of-unit review, math centers, early finishers, sub plans and homework. Completely no prep — just print and go.
The school pet has vanished from the classroom pet corner overnight, and fifteen pets are listed in the care logbook. Students work through five math clue pages and use every answer to cross suspects off the chart — fur, color, name tag, size, then the pet number — until only one pet is left. Each clue reveals one detail about the missing pet, so the math has to be right for the case to solve. No apps, no locks, no student logins.
Every page comes in color and black-and-white, and full answer keys are included.
Skills Covered
- 3-digit subtraction with regrouping to break a coded message: 526 − 451, 855 − 765, 814 − 754
- 3-digit addition within 1,000 with regrouping, deciding whether each answer is correct or not: 392 + 211, 699 + 154, 534 + 418
- Multiplication and division facts within 100: 6 × 9, 7 × 10, 9 × 2, 36 ÷ 6, 70 ÷ 10, 21 ÷ 7
- Rounding 3-digit numbers to the nearest 10 and the nearest 100: 536, 154, 218, 852, 468, 331
- Multiplying one-digit numbers by multiples of 10: 4 × 40, 7 × 80, 2 × 90, 9 × 10
- Reading a suspect chart and using answers to eliminate suspects
- Logic, reasoning and careful checking to identify the culprit
What's Included
- The Missing School Pet case file and story page
- Five math clue pages, each one revealing a different detail about the missing pet
- A coded-message clue, a true-or-false tally clue, a draw-a-line matching clue, a shade-the-answer rounding clue and a path-tracing maze clue
- Suspect chart elimination activity
- Full answer keys for every page
- Color and black-and-white versions
- Print-and-go PDF format
What is a CSI Mystery Detective?
It is a print-and-solve math activity — like an escape room without the locks. Students work through math problems to collect evidence, eliminate suspects and reveal who did it. It combines real skill practice with critical thinking and a detective hook that keeps the whole class engaged.
When to Use This Resource
- Back-to-school and end-of-year math review
- Spiral review of the year's core 3rd grade skills
- Math centers and early finishers
- Substitute teacher plans
- Small groups and independent work
- Homework and homeschool math
- End-of-unit review before a test
Grade Levels
Designed for 3rd grade. Also beneficial for advanced 2nd graders ready for a challenge and for 4th graders who need a confidence-building review of addition, subtraction, multiplication, division and rounding.
Why Teachers Love CSI Mystery Detective packs
- Zero prep — print and hand out
- Self-checking: a wrong answer will not solve the case, so students spot their own mistakes
- Five different puzzle formats keep the pace up across a full review lesson
- Covers several standards in one activity instead of one skill at a time
- Works for whole class, partners, centers or independent work
- Color and black-and-white versions for any printer
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