Clue Solvers Worksheet CONFIDENTIAL // MATH UNIT 2
Math Detective Academy
CASE FILES [CUBES]
DETECTIVE: ________________________
DATE: ____________
CLASS: __________
The CUBES Investigation Protocol
C Circle key numbers & units (e.g., 3,450 stamps)
U Underline the core question being asked.
B Box action words that reveal operation clues.
E Eliminate extra details & numbers not needed.
S Solve & Check . Does your final answer make sense?
Clue Word Decoder
Addition
• Altogether
• In All / Total
• Combined
• More / Join
Subtraction
• Difference
• How many more
• Fewer / Left
• Decreased by
Warm-Up Investigation CASE ID: #101-STAMPS
The Postal Museum had 3,450 vintage stamps. They received a donation of 1,285 more stamps, but then found that 412 stamps were counterfeit. How many authentic stamps does the museum have now?
Execution Check
[ ] Circled Numbers [ ] Underlined Question [ ] Boxed Action Words [ ] Eliminated Extra Info
Operation Map
CLUE 1: "donation of" means:
ADD (+)
SUBTRACT (-)
CLUE 2: "counterfeit" means:
ADD (+)
SUBTRACT (-)
CRIME LAB WORKSPACE (SHOW REGROUPING)
The Official Verdict Solve & Check Result
The Postal Museum has authentic stamps.
ACTIVE CASEWORK
Investigations Page 2
Level: Multi-Digit Regrouping
Case File #102
A cargo ship arrived carrying 8,024 shipping crates. The deck crew unloaded 3,485 crates in the morning and 2,190 crates in the afternoon. How many crates are still left on the ship?
CUBES Steps:
[C] Circle # & units [U] Underline Q [B] Box clues [E] Eliminate info
CLUE TRANSLATOR
"unloaded" means:
ADD (+) SUBTRACT (-)
"still left" means:
ADD (+) SUBTRACT (-)
Plan: First add total unloaded, then subtract from start!
CRIME LAB: SHOW ALL REGROUPING
VERDICT: There are crates still left on the cargo ship.
[PAGE 2/2]
Case File #103
On Saturday, Adventure Island theme park welcomed 5,125 visitors. On Sunday, they had 1,340 fewer visitors than Saturday. What was the total number of visitors for both days combined?
CUBES Steps:
[C] Circle # & units [U] Underline Q [B] Box clues [E] Eliminate info
CLUE TRANSLATOR
"fewer" means:
ADD (+) SUBTRACT (-)
"total / combined" means:
ADD (+) SUBTRACT (-)
Plan: Step 1: Find Sunday. Step 2: Add Saturday & Sunday together!
CRIME LAB: SHOW ALL REGROUPING
VERDICT: The total number of visitors for both days combined was visitors.
[PAGE 2/2]
Clue Solvers Answer Key ANSWER KEY // TEACHER USE ONLY
Math Detective Academy Answer Key
CASE FILES [CUBES KEYS]
MASTER KEY: 5th Grade Math Unit 2
SUBJECT: Regrouping
STRATEGY: CUBES + Decoder
CUBES Marking Key Guide
The red markings on the right show how students should annotate the word problems. Make sure students complete the checklist below.
Circle: numbers & units (3,450 stamps)
Underline: questions (How many...)
Box: clue words (donation of)
Clue Word Decoder
Addition
• Altogether
• In All / Total
• Combined
• More / Join
Subtraction
• Difference
• How many more
• Fewer / Left
• Decreased by
Warm-Up Investigation - SOLVED CASE ID: #101-STAMPS
The Postal Museum had 3,450 vintage stamps. They received a donation of 1,285 more stamps, but then found that 412 stamps were counterfeit. How many authentic stamps does the museum have now?
Execution Check
[X] Circled Numbers
[X] Underlined Question
[X] Boxed Action Words
[X] Eliminated Extra Info
Operation Map
CLUE 1: "donation of" means:
ADD (+)
CLUE 2: "counterfeit" means:
SUBTRACT (-)
CRIME LAB WORKSPACE (SOLUTIONS)
STEP 1: ADD DONATION
1
3
4
5
0
stamps
1
2
8
5
stamps
4
7
3
5
total
STEP 2: SUBTRACT COUNTERFEIT
4
7
3
5
total
-
4
1
2
fake
4
3
2
3
auth.
The Official Verdict Solve & Check Result
The Postal Museum has 4,323 authentic stamps.
ACTIVE CASEWORK KEYS
Investigations Page 2 Keys
Level: Multi-Digit Regrouping
Case File #102
A cargo ship arrived carrying 8,024 shipping crates. The deck crew unloaded 3,485 crates in the morning and 2,190 crates in the afternoon. How many crates are still left on the ship?
Clue Solvers Teacher Guide FACILITATION BRIEFING // NO. 504
Teacher Facilitation Manual
Clue Solvers Teacher Guide
GRADE: 5th Grade
FOCUS: Addition & Subtraction
STRATEGY: CUBES Math
Mission Objective
Students will apply the CUBES strategy and translation mapping to dissect and solve multi-step, multi-digit addition and subtraction word problems with regrouping, tracking their thinking in a custom case file.
Strategic Anchoring
The CUBES system gives students concrete physical markings to prevent overload. Pairing this with the Decoder connects linguistics (e.g., "fewer than") directly to math operations before solving.
Misconception Alert
• Regrouping Over Zeros: Model borrowing step-by-step from neighbor columns in Case 102 (8,024).
• Premature Stopping: Remind students that in Case 103, finding Sunday's turnout is only Step 1.
Instructional Sequence & Pacing
Step 1: Academy Briefing (10 Mins) INTRO
Pass out Case Files. Frame students as "Math Detectives." Review the CUBES reference on Page 1.
Dialogue: "Why circle numbers? To isolate evidence. If we leave them in the block, they distract us!"
Step 2: Guided Warm-Up (15 Mins) GUIDED
Work through Case 101 together. Model annotating the prompt, decoding "donation of" (+) and "counterfeit" (-). Emphasize proper column alignment in the Crime Lab grid area to avoid regrouping errors.
Step 3: Active Investigations (20 Mins) PRACTICE
Have students solve Cases 102 & 103 in pairs or solo. Circulate to check subtraction borrowing in Case 102. Ensure they finish the full CUBES checkboxes before writing the Final Verdict.
Adaptive Support & Extension
Scaffolding (Support)
Have struggling students write vertical calculations on separate grid paper first to line up place values perfectly.
Differentiated Extensions
Challenge early finishers to construct their own "Case 104" with a partner, requiring two operations to solve.
UNIT 2 LESSON PLAN // DETECTIVE ADVISORY MATH DETECTIVE ACADEMY © 2026