Students investigate a fictional budget mystery by using decimal operations, ratio reasoning, patterns, and logical argument to determine what happened to the missing $500 and whether the records are accurate. Across the launch, daily clue analysis, partner revision talks, and final press conference or verdict day, they learn to support claims with math evidence, question faulty reasoning, and refine explanations over time. The experience builds content expertise and self-direction while requiring teams to communicate clearly, collaborate on decisions, and connect their first theory to a well-supported final case explanation.

Students will use decimal addition and subtraction within a $500 budget to track purchases, refunds, errors, and remaining balances, and use ratio and rate reasoning to compare amounts and identify patterns across clues. They will look for structure and repeated reasoning in tables, receipts, and spending records to test theories, revise claims, and explain why the totals do not match. Students will construct evidence-based arguments in teams, critique one another’s reasoning during partner shares and briefings, and clearly communicate a final explanation through a case file, evidence board, or slide presentation. They will also reflect on how collaboration, revision, and feedback shaped their investigation from first guess to final verdict.

Teams create working case notes each session that track clues, decimal calculations, ratio comparisons, revised theories, and a mystery budget timeline from first clue to verdict. Midway through the project, students build a courtroom evidence board or detective case file poster with receipts, tables, calculations, and a claim about who spent the most, who spent the least, and why the totals do not match. For the final product, each team produces either a press conference slide deck or a polished case review poster that compares their first guess to their final explanation and clearly shows the math steps proving what happened to the $500. These products support a live Detective Press Conference or Verdict Day presentation where students defend their reasoning, answer audience questions, and name one math skill and one collaboration skill they strengthened.

Stage a “Budget Crime Scene Reveal” by scattering fake receipts, a cash box, a spending log, and a posted note that says the class project fund is missing $500. In teams, students examine the evidence, notice mismatched totals, and record the first math pattern or inconsistency they can prove with decimal addition and subtraction. Pause for a whole-class detective huddle where teams share an initial theory about what happened, who may have spent the most or least, and what evidence they still need. Close with a quick partner share on what math supports their theory, what still seems off, and one revision they want to make next class.

Host a Detective Press Conference where teams present their case file poster, evidence board, or slide deck to families or school leaders, walking the audience through the clues, decimal calculations, receipt errors, and revised theories before answering questions about who spent the most, who spent the least, and why the budget did not match. End with a Missing $500 Verdict Day in a classroom courtroom, where each team gives a short oral briefing, defends its final explanation with math evidence, and compares its first guess to its final conclusion. Invite audience members to act as reporters or jurors who question the teams’ reasoning and collaboration choices. Display each team’s mystery budget timeline and case review so visitors can see how the investigation changed over time and what math and teamwork skills students strengthened.