Grade 4Reading: grades 3-4AdditionRoundingSubtractionMultiplicationDivision

Mystery of Thunder Island

Someone snuck into the Thunder Island camp and took the master map! The Treehouse Crew needs your math skills to figure out who took it.

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	Island Tool	Secret Badge	Compass Hand	Bandana Color	Trap Phobia
Pioneer Max	Signal Flare	Sun Medallion	Right Handed	Red Bandana	Scared Of Bees
Scout Jax	Signal Flare	Cloud Patch	Right Handed	Red Bandana	Scared Of Bees
Trailing Nora	Signal Flare	Wave Symbol	Right Handed	Red Bandana	Scared Of Bees
Hiker Toby	Grappling Hook	Cloud Patch	Right Handed	Blue Bandana	Scared Of Bees
Cap Sam	Grappling Hook	Wave Symbol	Right Handed	Gold Bandana	Scared Of Bats
Adventurer Maya	Rope Ladder	Star Crest	Right Handed	Gold Bandana	Scared Of Crabs
Finder Mia	Torch Light	Sun Medallion	Right Handed	Blue Bandana	Scared Of Crabs
Diver Kai	Brass Telescope	Moon Coin	Left Handed	Gold Bandana	Scared Of Bees
Wayfarer Ella	Grappling Hook	Sun Medallion	Right Handed	Gold Bandana	Scared Of Bees
Sailor Pip	Signal Flare	Star Crest	Left Handed	Gold Bandana	Scared Of Crabs
Surveyor Ruby	Signal Flare	Moon Coin	Right Handed	Gold Bandana	Scared Of Bees
Voyager Finn	Torch Light	Moon Coin	Right Handed	Blue Bandana	Scared Of Bats
Pathfinder Lily	Rope Ladder	Wave Symbol	Right Handed	Red Bandana	Scared Of Bats
Ranger Ava	Signal Flare	Cloud Patch	Left Handed	Red Bandana	Scared Of Bees
Hunter Chloe	Brass Telescope	Star Crest	Right Handed	Red Bandana	Scared Of Bees
Trekker Noah	Brass Telescope	Moon Coin	Left Handed	Gold Bandana	Scared Of Crabs
Explorer Ben	Rope Ladder	Moon Coin	Right Handed	Red Bandana	Scared Of Bees
Skipper Lou	Signal Flare	Cloud Patch	Right Handed	Gold Bandana	Scared Of Bees
Pioneer Ivy	Grappling Hook	Wave Symbol	Left Handed	Red Bandana	Scared Of Bees
Cartographer Eli	Rope Ladder	Sun Medallion	Right Handed	Gold Bandana	Scared Of Bats
Navigator Zoe	Grappling Hook	Wave Symbol	Left Handed	Blue Bandana	Scared Of Bats

Clue 1

Addition

You count the total gold coins found in two wooden chests to crack the first secret door lock.

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

5480

3569

4371

3626

4846

3240

2764

4846

6971

9235

5822

4371

7418

6971

5822

5480

3569

2764

3626

4371

2764

7418

5480

2764

8635

9222

8635

4371

7418

5480

2757 + 2723 =T

1380 + 2991 =E

4113 + 2858 =N

3753 + 2069 =O

3215 + 5420 =R

4160 + 5062 =C

2334 + 2512 =I

1339 + 2287 =V

4671 + 4564 =D

1251 + 2318 =H

1604 + 1160 =A

3526 + 3892 =S

1831 + 1409 =L

0/13 letters found

Clue 2

Rounding

A dusty ancient compass readout only shows rounded map coordinates to help you track the suspect.

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

1700

2000

1300

370

1700

5000

2000

2300

1700

2900

130

5000

1700

300

1300

200

2300

370

700

Round 74 to the nearest tenT

Round 368 to the nearest tenN

Round 2,855 to the nearest hundredM

Round 1,666 to the nearest hundredE

Round 346 to the nearest hundredR

Round 23 to the nearest tenA

Round 224 to the nearest hundredG

Round 128 to the nearest tenU

Round 1,666 to the nearest thousandW

Round 1,265 to the nearest hundredI

Round 689 to the nearest hundredD

Round 2,290 to the nearest hundredH

Round 5,485 to the nearest thousandS

0/13 letters found

Clue 3

Subtraction

You compare the total supply crates before and after the incident to see how much was taken.

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

4188

7228

5797

6355

5139

3638

4889

7228

6885

4642

6194

4188

6098

6885

6887

4416

6194

6885

1546

4800

1802

5693 - 1505 =A

6856 - 1967 =G

8154 - 2056 =S

5383 - 741 =C

5856 - 1440 =T

5143 - 343 =O

9369 - 2482 =D

7546 - 1749 =U

6757 - 3119 =N

7237 - 9 =B

8535 - 1650 =E

7390 - 1035 =Z

6473 - 4671 =F

2443 - 897 =M

7819 - 2680 =I

6963 - 769 =H

0/16 letters found

Clue 4

Multiplication facts (1-12)

The cavern wall has several equal rows of carved symbols that must be multiplied to open the passage.

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

110

132

110

132

120

2 × 1 =R

10 × 7 =D

11 × 10 =T

9 × 9 =N

9 × 7 =O

5 × 1 =B

10 × 9 =W

12 × 4 =E

8 × 7 =S

10 × 12 =C

11 × 12 =A

8 × 8 =H

0/12 letters found

Clue 5

Division facts (1-12) — the last clue

You divide the remaining trail markers equally among your team to search all path options.

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

63 ÷ 9 = ?

27 ÷ 3 = ?

36 ÷ 12 = ?

80 ÷ 8 = ?

8 ÷ 2 = ?

99 ÷ 9 = ?

20 ÷ 10 = ?

6 ÷ 1 = ?

48 ÷ 4 = ?

32 ÷ 4 = ?

10 ÷ 2 = ?

Step 2 — cross out the sentence with each answer

1.The villain lit a signal flare, then waved a wave symbol.

2.The villain dropped a rope ladder, then pinned on a cloud patch.

3.The villain lit a signal flare, then flashed a sun medallion.

4.The villain lit a signal flare, then dropped a moon coin.

5.The villain swung with a grappling hook, then flashed a sun medallion.

6.The villain dropped a rope ladder, then flashed a sun medallion.

7.The villain lit a signal flare, then pinned on a cloud patch.

8.The villain swung with a grappling hook, then showed a star crest.

9.The villain dropped a rope ladder, then dropped a moon coin.

10.The villain swung with a grappling hook, then waved a wave symbol.

11.The villain dropped a rope ladder, then showed a star crest.

12.The villain peered through a brass telescope, then showed a star crest.

Solve it

Name the culprit

Choose the one suspect left standing.

Answer Key — Mystery of Thunder Island

Culprit: Trailing Nora (Signal Flare · Wave Symbol · Right Handed · Red Bandana · Scared Of Bees)

Clue 1 (Addition): "THE VILLAIN DOES NOT HAVE A STAR CREST"
2757 + 2723 = 5480 (T) · 1380 + 2991 = 4371 (E) · 4113 + 2858 = 6971 (N) · 3753 + 2069 = 5822 (O) · 3215 + 5420 = 8635 (R) · 4160 + 5062 = 9222 (C) · 2334 + 2512 = 4846 (I) · 1339 + 2287 = 3626 (V) · 4671 + 4564 = 9235 (D) · 1251 + 2318 = 3569 (H) · 1604 + 1160 = 2764 (A) · 3526 + 3892 = 7418 (S) · 1831 + 1409 = 3240 (L)
Clue 2 (Rounding): "THE WITNESS SAW THEM USE A RIGHT HAND"
Round 74 to the nearest ten = 70 (T) · Round 368 to the nearest ten = 370 (N) · Round 2,855 to the nearest hundred = 2900 (M) · Round 1,666 to the nearest hundred = 1700 (E) · Round 346 to the nearest hundred = 300 (R) · Round 23 to the nearest ten = 20 (A) · Round 224 to the nearest hundred = 200 (G) · Round 128 to the nearest ten = 130 (U) · Round 1,666 to the nearest thousand = 2000 (W) · Round 1,265 to the nearest hundred = 1300 (I) · Round 689 to the nearest hundred = 700 (D) · Round 2,290 to the nearest hundred = 2300 (H) · Round 5,485 to the nearest thousand = 5000 (S)
Clue 3 (Subtraction): "A BUZZING BEE CHASED THEM OFF"
5693 - 1505 = 4188 (A) · 6856 - 1967 = 4889 (G) · 8154 - 2056 = 6098 (S) · 5383 - 741 = 4642 (C) · 5856 - 1440 = 4416 (T) · 5143 - 343 = 4800 (O) · 9369 - 2482 = 6887 (D) · 7546 - 1749 = 5797 (U) · 6757 - 3119 = 3638 (N) · 7237 - 9 = 7228 (B) · 8535 - 1650 = 6885 (E) · 7390 - 1035 = 6355 (Z) · 6473 - 4671 = 1802 (F) · 2443 - 897 = 1546 (M) · 7819 - 2680 = 5139 (I) · 6963 - 769 = 6194 (H)
Clue 4 (Multiplication facts (1-12)): "RED BANDANA THREADS WERE ON THE BRANCH"
2 × 1 = 2 (R) · 10 × 7 = 70 (D) · 11 × 10 = 110 (T) · 9 × 9 = 81 (N) · 9 × 7 = 63 (O) · 5 × 1 = 5 (B) · 10 × 9 = 90 (W) · 12 × 4 = 48 (E) · 8 × 7 = 56 (S) · 10 × 12 = 120 (C) · 11 × 12 = 132 (A) · 8 × 8 = 64 (H)
Clue 5 (Division facts (1-12)): surviving statement (box 1) → Trailing Nora
63 ÷ 9 = 7 · 27 ÷ 3 = 9 · 36 ÷ 12 = 3 · 80 ÷ 8 = 10 · 8 ÷ 2 = 4 · 99 ÷ 9 = 11 · 20 ÷ 10 = 2 · 6 ÷ 1 = 6 · 48 ÷ 4 = 12 · 32 ÷ 4 = 8 · 10 ÷ 2 = 5

About this mystery

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

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