Thanksgiving Decimals CSI Mystery Worksheets

Inside the case file

These Thanksgiving decimals worksheets give your 5th grade class one full CSI Mystery Detective math case on adding, subtracting and multiplying decimals, with comparing and rounding decimals worked in along the way. It has a Thanksgiving grocery store theme. Use it as a whole-class challenge, in math centers or for homework. There's no prep, and the answer key covers every page.

On the morning before Thanksgiving, every price tag at Harvest Hill Market has been swapped, and one of fifteen night-shift workers did it. Students sort scale stickers through a yes/no machine, match dropped price tags to shelf labels, fill in a logic grid, open a locker combination and plot a security camera's path on a coordinate grid. Each clue rules out some of the workers. Because a wrong decimal answer points at the wrong suspects, students can check their own decimal work as they go.

What Is a CSI Mystery Detective?

It's one longer detective story told over five clue pages. Students read the case file first. Then each clue page gives them some math, and the answer tells them one fact about the culprit, like their department or the color of their apron. They cross off the suspects on the chart who don't fit. After clue five, one name is left.

What's Inside

• One Thanksgiving case, The Price Tag Prankster, with a story page, a suspect chart of 15 workers and five clue pages
• Adding and subtracting decimals with money, including change from whole dollars, such as $23 - $4.31
• Multiplying decimals by whole numbers and by decimals: 3.5 lb at $4.30 a pound, 0.4 lb at $1.65 a pound
• Comparing decimals to the thousandths and rounding to the nearest whole number
• Plotting points on a coordinate grid. The coordinates come from decimal answers.
• A logic grid with four shoppers, four things they bought and four amounts of money
• Color and black and white copies of every page
• A complete answer key. The key's suspect chart shows which clue removes each worker.
• Teacher instructions. 30 pages in all.

The Clues

1. Clue One - a sorting machine: compare and round decimals to find the department
2. Clue Two - dropped price tags: multiply decimals and match each tag to a shelf label to find the apron color
3. Clue Three - four witnesses: a logic grid with money clues that gives the hat
4. Clue Four - six staff lockers: add and subtract money to find the combination and the shoes
5. Clue Five - the security camera: plot points to find the last digit of the employee number

When to Use This Resource

Use it in the days before Thanksgiving break, when you want decimal review that still feels like part of the holiday. You can hand out all five clues at once, or give your class one clue at a time and keep the suspect chart going between lessons. Partners and small groups can share a case and split the clue pages. It also works for sub plans, for 6th graders reviewing decimal operations, and for homeschool families who want a Thanksgiving math project.

Grade Levels

Written for 5th grade, where adding, subtracting and multiplying decimals (5.NBT.B.7) and the coordinate grid (5.G.A.1) are taught. 6th grade classes can use it for decimal operations review (6.NS.B.3).

Why Teachers Love Mystery Detectives

Each clue is a different kind of puzzle, from a machine to a logic grid to a locker, so the pages don't feel like five worksheets in a row. Students always know what they're working toward: the next clue and a shorter suspect list. When the class has a name, you can check it against the answer key in a few seconds.

Want more cases like these?

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