Grade 4Reading: grades 3-4RoundingAdditionSubtractionMultiplicationDivision

The Mystery of Sunken Island

The Sunken Island Explorer Camp is in chaos! Someone snuck into the map room and took the golden compass. Detective, check the footprints and decode the clues to catch the thief!

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	Main Tool	Extra Gear	Handedness	Hair Style	Clue Left Behind
Tracker Tom	Machete	Signal Flare	Right Handed	Curly Hair	Squeaky Boots
Scout Sam	Machete	Compass Case	Left Handed	Curly Hair	Shiny Belt
Officer Ollie	Machete	Signal Flare	Right Handed	Spiky Hair	Loud Whistle
Ranger Reed	Flashlight	Smoke Bomb	Right Handed	Curly Hair	Squeaky Boots
Tracker Tess	Grappling Hook	Compass Case	Right Handed	Curly Hair	Shiny Belt
Agent Alex	Binoculars	Compass Case	Left Handed	Curly Hair	Squeaky Boots
Explorer Leo	Machete	Signal Flare	Right Handed	Braided Hair	Squeaky Boots
Guide Grace	Binoculars	Compass Case	Right Handed	Spiky Hair	Squeaky Boots
Navigator Max	Binoculars	Canteen	Right Handed	Spiky Hair	Squeaky Boots
Scout Stella	Flashlight	Signal Flare	Right Handed	Curly Hair	Shiny Belt
Detective Dan	Flashlight	Smoke Bomb	Left Handed	Braided Hair	Shiny Belt
Rover Ryan	Binoculars	Compass Case	Left Handed	Spiky Hair	Squeaky Boots
Pilot Piper	Binoculars	Smoke Bomb	Left Handed	Spiky Hair	Shiny Belt
Pathfinder Pam	Decoder Ring	Canteen	Left Handed	Curly Hair	Shiny Belt
Navigator Nate	Grappling Hook	Compass Case	Right Handed	Curly Hair	Loud Whistle
Hunter Hannah	Grappling Hook	Smoke Bomb	Right Handed	Curly Hair	Squeaky Boots
Trekker Tim	Grappling Hook	Compass Case	Right Handed	Curly Hair	Squeaky Boots
Captain Clara	Machete	Signal Flare	Left Handed	Spiky Hair	Shiny Belt
Sailor Sarah	Machete	Compass Case	Right Handed	Spiky Hair	Loud Whistle
Guide Gina	Binoculars	Rope Ladder	Right Handed	Curly Hair	Squeaky Boots
Ranger Rick	Flashlight	Rope Ladder	Left Handed	Curly Hair	Squeaky Boots

Clue 1

Rounding

The map sensor only shows rounded distances to nearby tents. Round the radar numbers to narrow down where the thief fled.

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

3700

2900

300

3700

2900

1100

300

2000

5000

1100

5000

130

3700

300

370

1100

2300

370

900

2000

900

370

110

300

Round 3,718 to the nearest hundredT

Round 46 to the nearest tenU

Round 88 to the nearest tenS

Round 324 to the nearest hundredE

Round 886 to the nearest hundredL

Round 4,989 to the nearest thousandD

Round 19 to the nearest tenN

Round 2,914 to the nearest hundredH

Round 2,269 to the nearest hundredG

Round 130 to the nearest tenO

Round 368 to the nearest tenA

Round 110 to the nearest tenR

Round 2,065 to the nearest thousandF

Round 1,094 to the nearest hundredI

0/14 letters found

Clue 2

Addition

You combine the total gear packs collected from the jungle clearings to count up the evidence.

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

2864

4824

3988

2864

4824

5633

3988

5720

4180

3988

5720

2864

3058

2240

5633

8326

2864

8339

5720

2240

8638

8930

9454

2240

5633

4313

4824

2864

4824

9454

8326

8971

1885 + 979 =T

2382 + 1798 =L

2840 + 1984 =H

4541 + 4389 =M

1048 + 1192 =R

3334 + 4992 =N

2993 + 2640 =I

1597 + 2716 =G

3404 + 2316 =F

1743 + 2245 =E

4714 + 4257 =D

1977 + 1081 =P

4203 + 4435 =O

2619 + 5720 =S

4610 + 4844 =A

0/15 letters found

Clue 3

Subtraction

You check how many supplies remain in the camp chest to see what the thief took.

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

1835

1458

1041

4014

4643

4829

4643

4829

5792

4643

4375

2932

7498

4829

8711

6978

4643

4375

2176

5079

4824

1328

1041

4829

4375

1041

4014

1458

1589

5792

1041

5053 - 3218 =W

4935 - 921 =N

5864 - 72 =H

9887 - 2389 =D

6399 - 3467 =R

5207 - 3618 =G

2244 - 786 =I

8776 - 1798 =U

6763 - 1939 =B

5775 - 1132 =E

2741 - 1700 =T

13073 - 4362 =Q

6619 - 1540 =Y

1541 - 213 =O

6398 - 2023 =A

5626 - 3450 =K

6195 - 1366 =S

0/17 letters found

Clue 4

Multiplication facts (1-12)

The team finds equal rows of footprints along the mud path and counts them in groups.

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

120

100

108

121

110

108

110

100

108

110

10 × 12 =P

10 × 10 =L

11 × 10 =R

9 × 11 =I

12 × 9 =A

1 × 10 =T

3 × 11 =N

11 × 11 =S

4 × 12 =D

1 × 5 =F

9 × 9 =C

7 × 6 =U

8 × 9 =O

12 × 7 =E

3 × 6 =H

5 × 7 =Y

0/16 letters found

Clue 5

Division facts (1-12) — the last clue

You divide the total clue cards equally among the explorer squads to decode the final message.

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

6 ÷ 2 = ?

120 ÷ 10 = ?

10 ÷ 2 = ?

121 ÷ 11 = ?

70 ÷ 10 = ?

18 ÷ 2 = ?

10 ÷ 1 = ?

66 ÷ 11 = ?

20 ÷ 5 = ?

56 ÷ 7 = ?

6 ÷ 6 = ?

Step 2 — cross out the sentence with each answer

1.The villain cut through thick vines, then snatched the compass case.

2.The villain shined a bright flashlight, then dropped a smoke bomb.

3.The villain swung on a grappling hook, then dropped a smoke bomb.

4.The villain unlocked the vault ring, then snatched the compass case.

5.The villain scouted with binoculars, then scaled down a rope ladder.

6.The villain shined a bright flashlight, then scaled down a rope ladder.

7.The villain scouted with binoculars, then spilled a full canteen.

8.The villain cut through thick vines, then spilled a full canteen.

9.The villain unlocked the vault ring, then scaled down a rope ladder.

10.The villain unlocked the vault ring, then dropped a smoke bomb.

11.The villain scouted with binoculars, then shot off a signal flare.

12.The villain swung on a grappling hook, then snatched the compass case.

Solve it

Name the culprit

Choose the one suspect left standing.

Answer Key — The Mystery of Sunken Island

Culprit: Ranger Reed (Flashlight · Smoke Bomb · Right Handed · Curly Hair · Squeaky Boots)

Clue 1 (Rounding): "THE THIEF DID NOT USE A SIGNAL FLARE"
Round 3,718 to the nearest hundred = 3700 (T) · Round 46 to the nearest ten = 50 (U) · Round 88 to the nearest ten = 90 (S) · Round 324 to the nearest hundred = 300 (E) · Round 886 to the nearest hundred = 900 (L) · Round 4,989 to the nearest thousand = 5000 (D) · Round 19 to the nearest ten = 20 (N) · Round 2,914 to the nearest hundred = 2900 (H) · Round 2,269 to the nearest hundred = 2300 (G) · Round 130 to the nearest ten = 130 (O) · Round 368 to the nearest ten = 370 (A) · Round 110 to the nearest ten = 110 (R) · Round 2,065 to the nearest thousand = 2000 (F) · Round 1,094 to the nearest hundred = 1100 (I)
Clue 2 (Addition): "THE THIEF LEFT PRINTS FROM A RIGHT HAND"
1885 + 979 = 2864 (T) · 2382 + 1798 = 4180 (L) · 2840 + 1984 = 4824 (H) · 4541 + 4389 = 8930 (M) · 1048 + 1192 = 2240 (R) · 3334 + 4992 = 8326 (N) · 2993 + 2640 = 5633 (I) · 1597 + 2716 = 4313 (G) · 3404 + 2316 = 5720 (F) · 1743 + 2245 = 3988 (E) · 4714 + 4257 = 8971 (D) · 1977 + 1081 = 3058 (P) · 4203 + 4435 = 8638 (O) · 2619 + 5720 = 8339 (S) · 4610 + 4844 = 9454 (A)
Clue 3 (Subtraction): "WITNESSES HEARD SQUEAKY BOOTS AT NIGHT"
5053 - 3218 = 1835 (W) · 4935 - 921 = 4014 (N) · 5864 - 72 = 5792 (H) · 9887 - 2389 = 7498 (D) · 6399 - 3467 = 2932 (R) · 5207 - 3618 = 1589 (G) · 2244 - 786 = 1458 (I) · 8776 - 1798 = 6978 (U) · 6763 - 1939 = 4824 (B) · 5775 - 1132 = 4643 (E) · 2741 - 1700 = 1041 (T) · 13073 - 4362 = 8711 (Q) · 6619 - 1540 = 5079 (Y) · 1541 - 213 = 1328 (O) · 6398 - 2023 = 4375 (A) · 5626 - 3450 = 2176 (K) · 6195 - 1366 = 4829 (S)
Clue 4 (Multiplication facts (1-12)): "POLICE FOUND A STRAND OF CURLY HAIR"
10 × 12 = 120 (P) · 10 × 10 = 100 (L) · 11 × 10 = 110 (R) · 9 × 11 = 99 (I) · 12 × 9 = 108 (A) · 1 × 10 = 10 (T) · 3 × 11 = 33 (N) · 11 × 11 = 121 (S) · 4 × 12 = 48 (D) · 1 × 5 = 5 (F) · 9 × 9 = 81 (C) · 7 × 6 = 42 (U) · 8 × 9 = 72 (O) · 12 × 7 = 84 (E) · 3 × 6 = 18 (H) · 5 × 7 = 35 (Y)
Clue 5 (Division facts (1-12)): surviving statement (box 2) → Ranger Reed
6 ÷ 2 = 3 · 120 ÷ 10 = 12 · 10 ÷ 2 = 5 · 121 ÷ 11 = 11 · 70 ÷ 10 = 7 · 18 ÷ 2 = 9 · 10 ÷ 1 = 10 · 66 ÷ 11 = 6 · 20 ÷ 5 = 4 · 56 ÷ 7 = 8 · 6 ÷ 6 = 1

About this mystery

Grade level: Grade 4 math
Math topics: Rounding, Addition, Subtraction, Multiplication, Division
Reading level: grades 3-4
Theme: The Mystery of Sunken Island — set in Sunken Island Explorer Camp
Format: Interactive online & printable worksheet with answer key
Solution: One unique, verified culprit among 21 suspects

More free printable math cases

4th grade worksheets Addition worksheets Subtraction worksheets Multiplication worksheets Division worksheets Rounding worksheets All worksheets →

The Great Beacon Heist

Grade 4

The Whisker Haven Golden Fish Caper

Grade 4

The Great Ridge Mystery

Grade 4

The Mystery of Misty Mountain Trail

Grade 4