🔎 Math And geographyGrade 5Reading: grades 5-6AdditionSubtractionMultiplicationFractions of a numberDivision

The Great Meridian Mystery

Someone has scrambled the world's prime meridian marker inside the archives, throwing GPS coordinates across the globe into complete chaos! The Chief Cartographer needs your mathematical precision and map-reading skills to solve the clues and track down the culprit before we are lost forever.

Suspects

Possible suspects

Cross off a row as each clue rules it out. On screen, tap a row.

21 of 21 still in play

Name	Navigation Gear	Math Specialty	Marking Style	Wig Color	Navigation Error
Alexander Humboldt	brass compass	decimal masters	using blue ink	silver gray hair	rounding error
Carl Friedrich Gauss	laser rangefinder	fraction solvers	using blue ink	silver gray hair	scale mismatch
Amerigo Vespucci	brass compass	decimal masters	using red ink	ink black hair	magnetic drift
Sacagawea	laser rangefinder	topology wizards	using red ink	ink black hair	magnetic drift
Mary Somerville	laser rangefinder	algebra champions	using blue ink	silver gray hair	rounding error
Alan Turing	brass compass	fraction solvers	using blue ink	sandy brown hair	rounding error
Al Khwarizmi	topographic scanner	geometry experts	using blue ink	silver gray hair	rounding error
Grace Hopper	pocket sextant	algebra champions	using red ink	sandy brown hair	magnetic drift
Hypatia	topographic scanner	decimal masters	using blue ink	ink black hair	scale mismatch
Pythagoras	pocket sextant	topology wizards	using blue ink	sandy brown hair	rounding error
Gerardus Mercator	satellite receiver	algebra champions	using red ink	silver gray hair	rounding error
Eratosthenes	brass compass	algebra champions	using red ink	sandy brown hair	magnetic drift
Marco Polo	laser rangefinder	algebra champions	using blue ink	silver gray hair	magnetic drift
Katherine Johnson	laser rangefinder	fraction solvers	using red ink	silver gray hair	scale mismatch
Blaise Pascal	brass compass	geometry experts	using blue ink	silver gray hair	rounding error
Isaac Newton	laser rangefinder	decimal masters	using blue ink	ink black hair	scale mismatch
Jeanne Baret	pocket sextant	fraction solvers	using red ink	ink black hair	rounding error
Ada Lovelace	topographic scanner	decimal masters	using red ink	sandy brown hair	magnetic drift
Euclid	satellite receiver	fraction solvers	using red ink	sandy brown hair	scale mismatch
Ibn Battuta	satellite receiver	topology wizards	using blue ink	silver gray hair	scale mismatch
James Cook	topographic scanner	algebra champions	using blue ink	silver gray hair	rounding error

Clue 1

Addition

To trace the escape route across the continents, we must add up the total distance between the scrambled coordinates. Let us tally these values first.

Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.

3452

7207

6579

5135

9254

6818

8424

6028

5284

9547

6818

3452

6818

9547

6579

6818

4072

3452

7207

6579

8586

6579

5135

6028

3696

3499

4424

3696

3499

5284

3452

6579

9254

5284

1328 + 2124 =T

2714 + 4493 =H

6337 + 3210 =N

2523 + 2761 =S

3069 + 3510 =E

5745 + 3509 =R

1818 + 4210 =I

2414 + 1658 =F

3145 + 1990 =C

2171 + 2253 =L

2675 + 4143 =O

5117 + 3469 =D

1647 + 1852 =A

1216 + 2480 =M

4886 + 3538 =K

0/15 letters found

Clue 2

Subtraction

The suspect tampered with the altitude settings on our GPS tracking screen. Subtract the baseline elevation from the current peaks to isolate the real pathway.

Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.

4461

3214

6779

8001

3162

1884

2730

6779

3133

8001

6779

1423

6779

2730

5621

4159

3214

5621

8348

4038

4665

5565

6779

1884

1423

2140

2730

5621

3162

2140

3133

5356 - 895 =T

3297 - 1413 =I

8495 - 2930 =U

6228 - 3095 =S

5672 - 51 =A

11839 - 3838 =C

11302 - 2954 =D

4283 - 124 =P

3381 - 651 =M

11312 - 4533 =E

6510 - 2472 =B

5245 - 3822 =N

3861 - 1721 =K

6904 - 3742 =R

4995 - 1781 =H

6061 - 1396 =L

0/16 letters found

Clue 3

Multiplication facts (1-12)

The search grid is divided into neat rows and columns. Multiply the scale divisions of our target grid map to find out how many square units we must investigate.

Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.

132

7 × 9 =T

4 × 5 =H

11 × 12 =D

2 × 7 =F

1 × 1 =S

10 × 9 =I

11 × 7 =E

4 × 1 =C

9 × 2 =R

9 × 11 =O

7 × 7 =G

7 × 4 =A

5 × 1 =U

11 × 3 =N

0/14 letters found

Clue 4

Fractions of a number

Only a fraction of the historical map files in the secure drawer were altered by the intruder. Let us calculate this fraction of the total archive set to unlock the next clue.

Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.

3/6 of 28 =T

2/10 of 95 =N

3/6 of 34 =R

4/8 of 6 =I

1/2 of 42 =A

2/4 of 80 =E

2/8 of 60 =H

3/6 of 52 =L

1/5 of 80 =Y

2/8 of 92 =P

3/6 of 24 =G

4/10 of 85 =V

3/4 of 32 =D

1/5 of 50 =S

0/14 letters found

Clue 5

Division facts (1-12) — the last clue

We need to divide our search party evenly into regional tracking teams. Divide the total coordinate boundaries by the number of active teams to get our final search area.

First solve each problem. Then find each answer in the list below and cross that sentence out. One sentence will be left — that's exactly what the villain did!

Step 1 — solve these

77 ÷ 7 = ?

24 ÷ 6 = ?

42 ÷ 7 = ?

108 ÷ 12 = ?

50 ÷ 10 = ?

120 ÷ 10 = ?

20 ÷ 2 = ?

64 ÷ 8 = ?

42 ÷ 6 = ?

24 ÷ 12 = ?

33 ÷ 11 = ?

Step 2 — cross out the sentence with each answer

1.The villain measured the distance with a laser rangefinder, then solved riddles like algebra champions.

2.The villain mapped the chamber with a topographic scanner, then navigated the rooms like topology wizards.

3.The villain measured the distance with a laser rangefinder, then bragged about being fraction solvers.

4.The villain mapped the chamber with a topographic scanner, then solved riddles like algebra champions.

5.The villain oriented the vault map with a brass compass, then bragged about being fraction solvers.

6.The villain oriented the vault map with a brass compass, then proved they were skilled geometry experts.

7.The villain calculated angles using a pocket sextant, then solved riddles like algebra champions.

8.The villain measured the distance with a laser rangefinder, then declared themselves decimal masters.

9.The villain tracked the satellite receiver signal, then solved riddles like algebra champions.

10.The villain tracked the satellite receiver signal, then proved they were skilled geometry experts.

11.The villain mapped the chamber with a topographic scanner, then proved they were skilled geometry experts.

12.The villain tracked the satellite receiver signal, then declared themselves decimal masters.

Solve it

Name the culprit

Choose the one suspect left standing.

Answer Key — The Great Meridian Mystery

Culprit: Mary Somerville (laser rangefinder · algebra champions · using blue ink · silver gray hair · rounding error)

Clue 1 (Addition): "THE CROOK IS NOT ONE OF THE DECIMAL MASTERS"
1328 + 2124 = 3452 (T) · 2714 + 4493 = 7207 (H) · 6337 + 3210 = 9547 (N) · 2523 + 2761 = 5284 (S) · 3069 + 3510 = 6579 (E) · 5745 + 3509 = 9254 (R) · 1818 + 4210 = 6028 (I) · 2414 + 1658 = 4072 (F) · 3145 + 1990 = 5135 (C) · 2171 + 2253 = 4424 (L) · 2675 + 4143 = 6818 (O) · 5117 + 3469 = 8586 (D) · 1647 + 1852 = 3499 (A) · 1216 + 2480 = 3696 (M) · 4886 + 3538 = 8424 (K)
Clue 2 (Subtraction): "THE CRIME SCENE MAP HAD BLUE INK MARKS"
5356 - 895 = 4461 (T) · 3297 - 1413 = 1884 (I) · 8495 - 2930 = 5565 (U) · 6228 - 3095 = 3133 (S) · 5672 - 51 = 5621 (A) · 11839 - 3838 = 8001 (C) · 11302 - 2954 = 8348 (D) · 4283 - 124 = 4159 (P) · 3381 - 651 = 2730 (M) · 11312 - 4533 = 6779 (E) · 6510 - 2472 = 4038 (B) · 5245 - 3822 = 1423 (N) · 3861 - 1721 = 2140 (K) · 6904 - 3742 = 3162 (R) · 4995 - 1781 = 3214 (H) · 6061 - 1396 = 4665 (L)
Clue 3 (Multiplication facts (1-12)): "THE COORDINATES SUFFERED A ROUNDING ERROR"
7 × 9 = 63 (T) · 4 × 5 = 20 (H) · 11 × 12 = 132 (D) · 2 × 7 = 14 (F) · 1 × 1 = 1 (S) · 10 × 9 = 90 (I) · 11 × 7 = 77 (E) · 4 × 1 = 4 (C) · 9 × 2 = 18 (R) · 9 × 11 = 99 (O) · 7 × 7 = 49 (G) · 7 × 4 = 28 (A) · 5 × 1 = 5 (U) · 11 × 3 = 33 (N)
Clue 4 (Fractions of a number): "THE GATES PRESERVED SILVER GRAY HAIR STRANDS"
3/6 of 28 = 14 (T) · 2/10 of 95 = 19 (N) · 3/6 of 34 = 17 (R) · 4/8 of 6 = 3 (I) · 1/2 of 42 = 21 (A) · 2/4 of 80 = 40 (E) · 2/8 of 60 = 15 (H) · 3/6 of 52 = 26 (L) · 1/5 of 80 = 16 (Y) · 2/8 of 92 = 23 (P) · 3/6 of 24 = 12 (G) · 4/10 of 85 = 34 (V) · 3/4 of 32 = 24 (D) · 1/5 of 50 = 10 (S)
Clue 5 (Division facts (1-12)): surviving statement (box 1) → Mary Somerville
77 ÷ 7 = 11 · 24 ÷ 6 = 4 · 42 ÷ 7 = 6 · 108 ÷ 12 = 9 · 50 ÷ 10 = 5 · 120 ÷ 10 = 12 · 20 ÷ 2 = 10 · 64 ÷ 8 = 8 · 42 ÷ 6 = 7 · 24 ÷ 12 = 2 · 33 ÷ 11 = 3

About this mystery

Grade level: Grade 5 math
Math topics: Addition, Subtraction, Multiplication, Fractions of a number, Division
Reading level: grades 5-6
Theme: The Great Meridian Mystery — set in The Great Map Archives
Format: Interactive online & printable worksheet with answer key
Solution: One unique, verified culprit among 21 suspects

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