Grade 4Reading: grades 3-4MultiplicationAdditionSubtractionRoundingDivision

The Secret of Sunken Island

Someone scrambled the compass coordinates and hid the golden idol! Help Detective Maya crack the coded notes and catch the sneaky saboteur before the ship sails.

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	Gear Tool	Badge Skill	Strap Side	Hat Color	Distraction
Hiker Hank	Glider Pack	Rope Knotting	Right Strap	Blue Cap	Bright Lights
Sailor Sally	Grappling Hook	Rope Knotting	Right Strap	Red Cap	Squeaky Toys
Rover Rex	Pocket Compass	Camp Building	Right Strap	Red Cap	Bright Lights
Tracker Tom	Signal Flare	Cave Diving	Right Strap	Green Cap	Loud Whistles
Scout Ben	Glider Pack	Camp Building	Right Strap	Red Cap	Loud Whistles
Agent Amy	Decoder Ring	Cave Diving	Right Strap	Red Cap	Loud Whistles
Sailor Sid	Pocket Compass	Rope Knotting	Right Strap	Red Cap	Bright Lights
Navigator Nina	Glider Pack	Track Finding	Left Strap	Blue Cap	Bright Lights
Scout Sam	Glider Pack	Cave Diving	Right Strap	Red Cap	Loud Whistles
Scout Skye	Decoder Ring	Track Finding	Right Strap	Red Cap	Loud Whistles
Ranger Rick	Grappling Hook	Cave Diving	Left Strap	Blue Cap	Bright Lights
Hiker Holly	Decoder Ring	Track Finding	Left Strap	Blue Cap	Loud Whistles
Captain Cody	Decoder Ring	Map Reading	Left Strap	Red Cap	Squeaky Toys
Tracker Tara	Pocket Compass	Track Finding	Left Strap	Red Cap	Squeaky Toys
Ranger Rosa	Glider Pack	Map Reading	Right Strap	Red Cap	Loud Whistles
Navigator Nate	Glider Pack	Track Finding	Right Strap	Blue Cap	Bright Lights
Agent Artie	Pocket Compass	Camp Building	Left Strap	Red Cap	Bright Lights
Guide Leo	Pocket Compass	Track Finding	Left Strap	Green Cap	Squeaky Toys
Pilot Pete	Decoder Ring	Map Reading	Left Strap	Green Cap	Loud Whistles
Guide Greta	Signal Flare	Map Reading	Left Strap	Red Cap	Loud Whistles
Pilot Penny	Pocket Compass	Cave Diving	Right Strap	Green Cap	Loud Whistles

Clue 1

Multiplication facts (1-12)

Maya counts several supply crates packed in equal rows on the dock to decode the first 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.

100

144

4 × 8 =T

4 × 11 =V

1 × 12 =O

7 × 12 =S

8 × 3 =H

11 × 1 =L

12 × 12 =G

2 × 1 =R

4 × 5 =A

10 × 10 =B

2 × 11 =P

5 × 5 =E

10 × 1 =M

11 × 5 =N

3 × 1 =C

9 × 3 =I

3 × 5 =D

8 × 11 =U

0/18 letters found

Clue 2

Addition

Maya adds up the total miles logged in the expedition journals to unlock the second note.

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

9768

6547

3529

6977

7068

6977

9119

3529

3101

9768

6173

3529

3745

4085

6977

3745

8553

3745

2110

6173

9177

9768

6547

3745

4085

9177

2110

6547

9768

6977

9768

4085

3745

9119

3972 + 5796 =T

6246 + 2931 =I

1352 + 2177 =E

4459 + 2088 =H

1216 + 894 =G

1712 + 2373 =R

3811 + 5308 =P

1203 + 2542 =A

4756 + 2221 =S

2702 + 4366 =U

2554 + 3619 =W

3573 + 4980 =B

1155 + 1946 =C

0/13 letters found

Clue 3

Subtraction

Maya calculates how many canteen refills remain after a day on the trail to reveal the third hint.

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

8340

5249

6438

1220

6072

8524

8695

8532

7866

8340

1220

4810

3429

6438

8532

6438

3105

6438

3434

8532

3769

3434

8340

8524

4810

6072

3105

6874

5249

7866

3769

8340

8524

6438

3769

9584 - 1244 =T

13390 - 4695 =P

5817 - 1007 =O

3432 - 327 =D

5804 - 555 =H

11613 - 3747 =I

10225 - 3351 =W

5838 - 2404 =A

8310 - 4541 =S

9425 - 3353 =U

6340 - 2911 =V

3958 - 2738 =C

10262 - 1738 =L

6501 - 63 =E

9977 - 1445 =R

0/15 letters found

Clue 4

Rounding

The digital scanner on the boat bridge only shows rounded altitude numbers for the fourth 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.

2300

500

4300

230

3700

230

2300

2000

300

5000

3000

2300

500

110

2000

3700

230

3000

2000

130

2000

1300

2900

3000

3700

Round 2,310 to the nearest hundredF

Round 2,858 to the nearest hundredS

Round 227 to the nearest tenD

Round 458 to the nearest hundredO

Round 2,096 to the nearest thousandA

Round 4,580 to the nearest thousandI

Round 1,293 to the nearest hundredT

Round 127 to the nearest tenP

Round 343 to the nearest hundredB

Round 88 to the nearest tenN

Round 112 to the nearest tenM

Round 4,333 to the nearest hundredU

Round 2,668 to the nearest thousandC

Round 3,736 to the nearest hundredE

Round 32 to the nearest tenR

0/15 letters found

Clue 5

Division facts (1-12) — the last clue

Maya splits the remaining energy bars equally among the scout patrols to decode the final clue.

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

30 ÷ 5 = ?

72 ÷ 8 = ?

110 ÷ 11 = ?

96 ÷ 8 = ?

77 ÷ 11 = ?

10 ÷ 2 = ?

7 ÷ 7 = ?

20 ÷ 10 = ?

30 ÷ 10 = ?

88 ÷ 8 = ?

24 ÷ 6 = ?

Step 2 — cross out the sentence with each answer

1.The villain swung across the ravine with a grappling hook, then set up a quick shelter with camp building.

2.The villain checked the direction with a pocket compass, then tied up the cargo using rope knotting.

3.The villain unlocked the ancient chest using a decoder ring, then used map reading to find the hidden path.

4.The villain soared past the jungle trees with a glider pack, then followed fresh footprints using track finding.

5.The villain swung across the ravine with a grappling hook, then used map reading to find the hidden path.

6.The villain unlocked the ancient chest using a decoder ring, then searched underwater tunnels with cave diving.

7.The villain shot a bright signal flare into the sky, then tied up the cargo using rope knotting.

8.The villain soared past the jungle trees with a glider pack, then used map reading to find the hidden path.

9.The villain unlocked the ancient chest using a decoder ring, then followed fresh footprints using track finding.

10.The villain soared past the jungle trees with a glider pack, then searched underwater tunnels with cave diving.

11.The villain unlocked the ancient chest using a decoder ring, then tied up the cargo using rope knotting.

12.The villain shot a bright signal flare into the sky, then set up a quick shelter with camp building.

Solve it

Name the culprit

Choose the one suspect left standing.

Answer Key — The Secret of Sunken Island

Culprit: Ranger Rosa (Glider Pack · Map Reading · Right Strap · Red Cap · Loud Whistles)

Clue 1 (Multiplication facts (1-12)): "THE SABOTEUR DOES NOT HAVE CAMP BUILDING"
4 × 8 = 32 (T) · 4 × 11 = 44 (V) · 1 × 12 = 12 (O) · 7 × 12 = 84 (S) · 8 × 3 = 24 (H) · 11 × 1 = 11 (L) · 12 × 12 = 144 (G) · 2 × 1 = 2 (R) · 4 × 5 = 20 (A) · 10 × 10 = 100 (B) · 2 × 11 = 22 (P) · 5 × 5 = 25 (E) · 10 × 1 = 10 (M) · 11 × 5 = 55 (N) · 3 × 1 = 3 (C) · 9 × 3 = 27 (I) · 3 × 5 = 15 (D) · 8 × 11 = 88 (U)
Clue 2 (Addition): "THE SUSPECT WEARS A BAG WITH A RIGHT STRAP"
3972 + 5796 = 9768 (T) · 6246 + 2931 = 9177 (I) · 1352 + 2177 = 3529 (E) · 4459 + 2088 = 6547 (H) · 1216 + 894 = 2110 (G) · 1712 + 2373 = 4085 (R) · 3811 + 5308 = 9119 (P) · 1203 + 2542 = 3745 (A) · 4756 + 2221 = 6977 (S) · 2702 + 4366 = 7068 (U) · 2554 + 3619 = 6173 (W) · 3573 + 4980 = 8553 (B) · 1155 + 1946 = 3101 (C)
Clue 3 (Subtraction): "THE CULPRIT COVERED EARS AT LOUD WHISTLES"
9584 - 1244 = 8340 (T) · 13390 - 4695 = 8695 (P) · 5817 - 1007 = 4810 (O) · 3432 - 327 = 3105 (D) · 5804 - 555 = 5249 (H) · 11613 - 3747 = 7866 (I) · 10225 - 3351 = 6874 (W) · 5838 - 2404 = 3434 (A) · 8310 - 4541 = 3769 (S) · 9425 - 3353 = 6072 (U) · 6340 - 2911 = 3429 (V) · 3958 - 2738 = 1220 (C) · 10262 - 1738 = 8524 (L) · 6501 - 63 = 6438 (E) · 9977 - 1445 = 8532 (R)
Clue 4 (Rounding): "FOUND RED FABRIC FROM A RED CAP AT SCENE"
Round 2,310 to the nearest hundred = 2300 (F) · Round 2,858 to the nearest hundred = 2900 (S) · Round 227 to the nearest ten = 230 (D) · Round 458 to the nearest hundred = 500 (O) · Round 2,096 to the nearest thousand = 2000 (A) · Round 4,580 to the nearest thousand = 5000 (I) · Round 1,293 to the nearest hundred = 1300 (T) · Round 127 to the nearest ten = 130 (P) · Round 343 to the nearest hundred = 300 (B) · Round 88 to the nearest ten = 90 (N) · Round 112 to the nearest ten = 110 (M) · Round 4,333 to the nearest hundred = 4300 (U) · Round 2,668 to the nearest thousand = 3000 (C) · Round 3,736 to the nearest hundred = 3700 (E) · Round 32 to the nearest ten = 30 (R)
Clue 5 (Division facts (1-12)): surviving statement (box 8) → Ranger Rosa
30 ÷ 5 = 6 · 72 ÷ 8 = 9 · 110 ÷ 11 = 10 · 96 ÷ 8 = 12 · 77 ÷ 11 = 7 · 10 ÷ 2 = 5 · 7 ÷ 7 = 1 · 20 ÷ 10 = 2 · 30 ÷ 10 = 3 · 88 ÷ 8 = 11 · 24 ÷ 6 = 4

About this mystery

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

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