Grade 4Reading: grades 3-4SubtractionRoundingAdditionMultiplicationDivision

The Coconut Island Mystery

The grand Golden Pineapple Trophy has vanished from the Island Club treehouse! The Island Club President needs your help. Solve the math puzzles to track down the mischievous thief before the big beach feast tonight.

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	Adventure Skill	Favorite Gear	Writing Hand	Hair Color	Biggest Fear
Sam	slingshot expert	waterproof walkie-talkie	right-handed writer	bright red hair	scared of spiders
Chloe	master climber	waterproof walkie-talkie	left-handed writer	dark brown hair	scared of spiders
Lily	slingshot expert	high-bounce boots	left-handed writer	bright red hair	hates muddy shoes
Ella	grappling hook thrower	glow-in-the-dark compass	right-handed writer	bright red hair	allergic to pollen
Owen	master climber	glow-in-the-dark compass	right-handed writer	golden blonde hair	allergic to pollen
Cole	master climber	all-terrain skateboard	left-handed writer	bright red hair	scared of spiders
Mason	speedy decoder	waterproof walkie-talkie	right-handed writer	dark brown hair	scared of spiders
Jack	slingshot expert	all-terrain skateboard	right-handed writer	bright red hair	allergic to pollen
Zoe	speedy decoder	all-terrain skateboard	right-handed writer	bright red hair	scared of spiders
Toby	grappling hook thrower	super-zoom binoculars	right-handed writer	bright red hair	hates muddy shoes
Maya	speedy decoder	glow-in-the-dark compass	right-handed writer	bright red hair	allergic to pollen
Luke	expert trail marker	high-bounce boots	left-handed writer	golden blonde hair	allergic to pollen
Finn	grappling hook thrower	waterproof walkie-talkie	right-handed writer	bright red hair	scared of spiders
Sophie	master climber	high-bounce boots	right-handed writer	bright red hair	scared of spiders
Noah	slingshot expert	waterproof walkie-talkie	right-handed writer	bright red hair	allergic to pollen
Ruby	expert trail marker	high-bounce boots	left-handed writer	bright red hair	hates muddy shoes
Leo	slingshot expert	glow-in-the-dark compass	left-handed writer	bright red hair	hates muddy shoes
Lucy	master climber	all-terrain skateboard	left-handed writer	golden blonde hair	allergic to pollen
Grace	slingshot expert	all-terrain skateboard	left-handed writer	golden blonde hair	hates muddy shoes
Ava	expert trail marker	glow-in-the-dark compass	right-handed writer	golden blonde hair	scared of spiders
Emma	speedy decoder	super-zoom binoculars	right-handed writer	bright red hair	scared of spiders

Clue 1

Subtraction

The spy team counted the walkie-talkies. We started with many but some are missing now. Subtract the stolen ones to find our 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.

4630

2358

4316

3533

5470

3745

1641

1915

4630

1641

3727

4316

3814

3745

3727

4630

4132

4316

5470

5681

2358

1915

7916

2358

3533

3727

5848

3745

5120

4316

3533

3727

4630

3814

5822 - 1192 =T

6646 - 2919 =O

10712 - 4864 =U

7441 - 1971 =A

4769 - 2411 =H

5781 - 2036 =N

8224 - 2543 =R

8941 - 1025 =G

4769 - 637 =W

8439 - 4625 =S

6314 - 1998 =E

5687 - 4046 =D

10020 - 4900 =C

3702 - 1787 =I

7406 - 3873 =B

0/15 letters found

Clue 2

Rounding

The jungle radar is old. It only shows distances rounded to the nearest ten. Round the signal number to unlock the next file.

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

1700

3000

7000

2300

1700

430

700

3000

130

290

1300

2300

290

200

1700

3700

290

430

3000

1700

290

430

700

2300

3700

290

370

700

430

700

2300

200

170

Round 1,672 to the nearest hundredW

Round 431 to the nearest tenT

Round 2,325 to the nearest hundredA

Round 1,313 to the nearest hundredL

Round 3,286 to the nearest thousandE

Round 193 to the nearest hundredN

Round 370 to the nearest tenG

Round 131 to the nearest tenV

Round 3,683 to the nearest hundredR

Round 7,170 to the nearest thousandS

Round 292 to the nearest tenI

Round 168 to the nearest tenD

Round 687 to the nearest hundredH

0/13 letters found

Clue 3

Addition

We found gold coins dropped along the beach trail. Add the coins from the sand and the grass to get the total number.

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

2099

3144

4317

2099

3144

7245

4317

3409

2933

5947

4251

5947

2727

5947

2986

3409

2933

3736

9339

5947

2099

7245

4251

2986

2606

6646

7245

8656

4317

2933

1231 + 868 =T

1175 + 1552 =W

2767 + 1484 =N

2007 + 979 =Y

1438 + 1706 =H

1723 + 1210 =R

4983 + 2262 =I

5986 + 2670 =D

2349 + 1060 =F

3170 + 6169 =M

2613 + 1704 =E

2388 + 1348 =O

1749 + 857 =S

3409 + 2538 =A

3780 + 2866 =P

0/15 letters found

Clue 4

Multiplication facts (1-12)

The ancient stone door has rows of matching carvings. Multiply the rows by the columns to press the right tiles.

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

108

121

108

120

108

9 × 12 =A

9 × 9 =R

6 × 6 =H

9 × 8 =E

8 × 12 =C

2 × 7 =S

10 × 12 =I

11 × 11 =D

3 × 11 =F

9 × 5 =B

6 × 9 =N

2 × 4 =O

11 × 1 =W

11 × 4 =T

0/14 letters found

Clue 5

Division facts (1-12) — the last clue

We need to share our juice boxes equally among the search teams. Divide the total boxes to find each team's share.

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

42 ÷ 7 = ?

24 ÷ 2 = ?

20 ÷ 4 = ?

81 ÷ 9 = ?

63 ÷ 9 = ?

110 ÷ 10 = ?

100 ÷ 10 = ?

20 ÷ 5 = ?

80 ÷ 10 = ?

4 ÷ 2 = ?

15 ÷ 5 = ?

Step 2 — cross out the sentence with each answer

1.The villain grabbed the secret island map, then zipped down the muddy jungle trail.

2.The villain stole the shiny compass medal, then scooted across the rickety wooden bridge.

3.The villain pocketed the ancient brass key, then zipped down the muddy jungle trail.

4.The villain took the legendary crystal skull, then zipped down the muddy jungle trail.

5.The villain pocketed the ancient brass key, then dashed away through the banana trees.

6.The villain snatched the golden pineapple trophy, then dashed away through the banana trees.

7.The villain snatched the golden pineapple trophy, then scooted across the rickety wooden bridge.

8.The villain stole the shiny compass medal, then zipped down the muddy jungle trail.

9.The villain pocketed the ancient brass key, then escaped in a yellow rubber raft.

10.The villain snatched the golden pineapple trophy, then escaped in a yellow rubber raft.

11.The villain grabbed the secret island map, then escaped in a yellow rubber raft.

12.The villain grabbed the secret island map, then scooted across the rickety wooden bridge.

Solve it

Name the culprit

Choose the one suspect left standing.

Answer Key — The Coconut Island Mystery

Culprit: Emma (speedy decoder · super-zoom binoculars · right-handed writer · bright red hair · scared of spiders)

Clue 1 (Subtraction): "THE BANDIT DOES NOT WEAR HIGH BOUNCE BOOTS"
5822 - 1192 = 4630 (T) · 6646 - 2919 = 3727 (O) · 10712 - 4864 = 5848 (U) · 7441 - 1971 = 5470 (A) · 4769 - 2411 = 2358 (H) · 5781 - 2036 = 3745 (N) · 8224 - 2543 = 5681 (R) · 8941 - 1025 = 7916 (G) · 4769 - 637 = 4132 (W) · 8439 - 4625 = 3814 (S) · 6314 - 1998 = 4316 (E) · 5687 - 4046 = 1641 (D) · 10020 - 4900 = 5120 (C) · 3702 - 1787 = 1915 (I) · 7406 - 3873 = 3533 (B)
Clue 2 (Rounding): "WE SAW THE VILLAIN WRITE WITH A RIGHT HAND"
Round 1,672 to the nearest hundred = 1700 (W) · Round 431 to the nearest ten = 430 (T) · Round 2,325 to the nearest hundred = 2300 (A) · Round 1,313 to the nearest hundred = 1300 (L) · Round 3,286 to the nearest thousand = 3000 (E) · Round 193 to the nearest hundred = 200 (N) · Round 370 to the nearest ten = 370 (G) · Round 131 to the nearest ten = 130 (V) · Round 3,683 to the nearest hundred = 3700 (R) · Round 7,170 to the nearest thousand = 7000 (S) · Round 292 to the nearest ten = 290 (I) · Round 168 to the nearest ten = 170 (D) · Round 687 to the nearest hundred = 700 (H)
Clue 3 (Addition): "THE THIEF RAN AWAY FROM A TINY SPIDER"
1231 + 868 = 2099 (T) · 1175 + 1552 = 2727 (W) · 2767 + 1484 = 4251 (N) · 2007 + 979 = 2986 (Y) · 1438 + 1706 = 3144 (H) · 1723 + 1210 = 2933 (R) · 4983 + 2262 = 7245 (I) · 5986 + 2670 = 8656 (D) · 2349 + 1060 = 3409 (F) · 3170 + 6169 = 9339 (M) · 2613 + 1704 = 4317 (E) · 2388 + 1348 = 3736 (O) · 1749 + 857 = 2606 (S) · 3409 + 2538 = 5947 (A) · 3780 + 2866 = 6646 (P)
Clue 4 (Multiplication facts (1-12)): "A STRAND OF RED HAIR WAS ON THE BRANCH"
9 × 12 = 108 (A) · 9 × 9 = 81 (R) · 6 × 6 = 36 (H) · 9 × 8 = 72 (E) · 8 × 12 = 96 (C) · 2 × 7 = 14 (S) · 10 × 12 = 120 (I) · 11 × 11 = 121 (D) · 3 × 11 = 33 (F) · 9 × 5 = 45 (B) · 6 × 9 = 54 (N) · 2 × 4 = 8 (O) · 11 × 1 = 11 (W) · 11 × 4 = 44 (T)
Clue 5 (Division facts (1-12)): surviving statement (box 1) → Emma
42 ÷ 7 = 6 · 24 ÷ 2 = 12 · 20 ÷ 4 = 5 · 81 ÷ 9 = 9 · 63 ÷ 9 = 7 · 110 ÷ 10 = 11 · 100 ÷ 10 = 10 · 20 ÷ 5 = 4 · 80 ÷ 10 = 8 · 4 ÷ 2 = 2 · 15 ÷ 5 = 3

About this mystery

Grade level: Grade 4 math
Math topics: Subtraction, Rounding, Addition, Multiplication, Division
Reading level: grades 3-4
Theme: The Coconut Island Mystery — set in a sunny tropical island with secret treehouse bases
Format: Interactive online & printable worksheet with answer key
Solution: One unique, verified culprit among 21 suspects

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