🌊 MermaidsGrade 4Reading: grades 3-4RoundingAdditionSubtractionMultiplicationDivision

The Case of the Missing Pearl

Someone has stolen the Magic Rainbow Pearl from the Royal Shell! Without it, Pearl Cove will lose its warm glow. As the chief sea detective, you must follow the clues and find the bubble-burglar before the lights go out.

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	ocean magic	sea animal ally	swimming style	seaweed crown	allergic to
Andrina	wave control	turtle ride	left fin swimmer	golden sea-grass	noisy clam snaps
Nixie	current speed	crab guard	left fin swimmer	golden sea-grass	sour lemon-kelp
Alana	current speed	dolphin scout	left fin swimmer	golden sea-grass	noisy clam snaps
Aquata	bubble shield	turtle ride	left fin swimmer	bright red algae	noisy clam snaps
Pearl	tide whisper	turtle ride	right fin swimmer	golden sea-grass	noisy clam snaps
Mimmi	tide whisper	crab guard	left fin swimmer	golden sea-grass	noisy clam snaps
Lyla	coral growth	turtle ride	left fin swimmer	golden sea-grass	noisy clam snaps
Arista	bubble shield	dolphin scout	left fin swimmer	golden sea-grass	noisy clam snaps
Rikki	current speed	turtle ride	left fin swimmer	golden sea-grass	noisy clam snaps
Adella	bubble shield	jellyfish light	right fin swimmer	bright red algae	sour lemon-kelp
Marina	current speed	turtle ride	right fin swimmer	bright red algae	noisy clam snaps
Sirena	coral growth	crab guard	right fin swimmer	golden sea-grass	tickly sea urchins
Emma	tide whisper	jellyfish light	left fin swimmer	neon green kelp	sour lemon-kelp
Bella	current speed	crab guard	right fin swimmer	bright red algae	noisy clam snaps
Ariel	current speed	dolphin scout	right fin swimmer	golden sea-grass	noisy clam snaps
Melody	current speed	turtle ride	left fin swimmer	bright red algae	noisy clam snaps
Waverly	current speed	crab guard	right fin swimmer	golden sea-grass	tickly sea urchins
Nerida	wave control	crab guard	right fin swimmer	bright red algae	tickly sea urchins
Attina	wave control	jellyfish light	left fin swimmer	golden sea-grass	sour lemon-kelp
Cleo	current speed	octopus helper	right fin swimmer	neon green kelp	sour lemon-kelp
Shelly	bubble shield	turtle ride	left fin swimmer	golden sea-grass	sour lemon-kelp

Clue 1

Rounding

Our submarine radar only shows rounded numbers. We must round the sonar pings to find where the thief went.

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

4300

430

3700

370

230

370

1100

4300

230

1100

1300

900

1300

4300

370

1100

290

1300

1700

Round 1,737 to the nearest hundredT

Round 3,741 to the nearest hundredV

Round 89 to the nearest tenS

Round 1,149 to the nearest hundredN

Round 293 to the nearest tenC

Round 24 to the nearest tenP

Round 371 to the nearest tenI

Round 33 to the nearest tenL

Round 430 to the nearest tenE

Round 226 to the nearest tenA

Round 52 to the nearest tenU

Round 864 to the nearest hundredD

Round 1,251 to the nearest hundredO

Round 4,343 to the nearest hundredH

0/14 letters found

Clue 2

Addition

We found three bags of stolen pearls on the seafloor. Let's add them up to find 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.

5220

9655

7636

3221

6988

8911

3516

6988

2619

8515

4677

6988

3523

8515

4677

6988

5220

9655

5220

9655

7636

6988

4944

8911

7636

3507

5220

3507

6988

2619

2421 + 2799 =T

1072 + 2149 =V

878 + 1741 =N

2863 + 1814 =W

4093 + 3543 =E

2146 + 1377 =M

2362 + 1154 =A

2442 + 2502 =R

5386 + 3129 =S

3586 + 5325 =L

1698 + 1809 =F

3570 + 6085 =H

4629 + 2359 =I

0/13 letters found

Clue 3

Subtraction

The thief dropped a chest of sea coins. Subtract the broken coins from the total to solve this part.

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

5872

3531

2105

8903

8399

6606

1886

2109

7602

8903

5872

2109

2363

8903

5421

2105

1886

8903

6606

2109

8607

1326

2429

1784

1326

8607

3531

4496

1326

8607

10221 - 4349 =N

8189 - 1583 =C

6507 - 2011 =B

5388 - 3025 =P

6916 - 4811 =I

12140 - 3237 =S

7420 - 4991 =T

10363 - 4942 =W

2900 - 791 =A

2516 - 732 =H

10935 - 2328 =R

8583 - 184 =Y

10966 - 3364 =M

4858 - 2972 =L

5586 - 4260 =E

7160 - 3629 =O

0/16 letters found

Clue 4

Multiplication facts (1-12)

The path is blocked by rows of glowing jellyfish. Multiply the rows to find a safe way through.

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

144

121

7 × 2 =G

5 × 7 =W

9 × 8 =L

11 × 6 =E

7 × 7 =O

7 × 8 =F

5 × 12 =I

10 × 7 =S

6 × 5 =A

9 × 9 =R

3 × 5 =N

11 × 11 =H

12 × 12 =T

2 × 2 =D

0/14 letters found

Clue 5

Division facts (1-12) — the last clue

We need to split our bubble-juices equally among the team to keep swimming. Divvy them up to crack 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

63 ÷ 7 = ?

70 ÷ 10 = ?

72 ÷ 6 = ?

50 ÷ 10 = ?

16 ÷ 2 = ?

120 ÷ 12 = ?

121 ÷ 11 = ?

6 ÷ 1 = ?

36 ÷ 12 = ?

12 ÷ 3 = ?

10 ÷ 5 = ?

Step 2 — cross out the sentence with each answer

1.The villain creates a wild wave control, then swims away on a turtle ride.

2.The villain speeds up the coral growth, then blocks the path with a crab guard.

3.The villain whispers a magic tide whisper, then swims away on a turtle ride.

4.The villain creates a wild wave control, then blocks the path with a crab guard.

5.The villain creates a wild wave control, then grabs the loot with an octopus helper.

6.The villain conjures a bubble shield, then escapes with a dolphin scout.

7.The villain speeds up the coral growth, then swims away on a turtle ride.

8.The villain activates a fast current speed, then sees in the dark with a jellyfish light.

9.The villain whispers a magic tide whisper, then blocks the path with a crab guard.

10.The villain creates a wild wave control, then sees in the dark with a jellyfish light.

11.The villain conjures a bubble shield, then sees in the dark with a jellyfish light.

12.The villain activates a fast current speed, then swims away on a turtle ride.

Solve it

Name the culprit

Choose the one suspect left standing.

Answer Key — The Case of the Missing Pearl

Culprit: Andrina (wave control · turtle ride · left fin swimmer · golden sea-grass · noisy clam snaps)

Clue 1 (Rounding): "THE VILLAIN HAS NO DOLPHIN SCOUT"
Round 1,737 to the nearest hundred = 1700 (T) · Round 3,741 to the nearest hundred = 3700 (V) · Round 89 to the nearest ten = 90 (S) · Round 1,149 to the nearest hundred = 1100 (N) · Round 293 to the nearest ten = 290 (C) · Round 24 to the nearest ten = 20 (P) · Round 371 to the nearest ten = 370 (I) · Round 33 to the nearest ten = 30 (L) · Round 430 to the nearest ten = 430 (E) · Round 226 to the nearest ten = 230 (A) · Round 52 to the nearest ten = 50 (U) · Round 864 to the nearest hundred = 900 (D) · Round 1,251 to the nearest hundred = 1300 (O) · Round 4,343 to the nearest hundred = 4300 (H)
Clue 2 (Addition): "THE VILLAIN SWIMS WITH THEIR LEFT FIN"
2421 + 2799 = 5220 (T) · 1072 + 2149 = 3221 (V) · 878 + 1741 = 2619 (N) · 2863 + 1814 = 4677 (W) · 4093 + 3543 = 7636 (E) · 2146 + 1377 = 3523 (M) · 2362 + 1154 = 3516 (A) · 2442 + 2502 = 4944 (R) · 5386 + 3129 = 8515 (S) · 3586 + 5325 = 8911 (L) · 1698 + 1809 = 3507 (F) · 3570 + 6085 = 9655 (H) · 4629 + 2359 = 6988 (I)
Clue 3 (Subtraction): "NOISY CLAM SNAPS WILL SCARE THE ROBBER"
10221 - 4349 = 5872 (N) · 8189 - 1583 = 6606 (C) · 6507 - 2011 = 4496 (B) · 5388 - 3025 = 2363 (P) · 6916 - 4811 = 2105 (I) · 12140 - 3237 = 8903 (S) · 7420 - 4991 = 2429 (T) · 10363 - 4942 = 5421 (W) · 2900 - 791 = 2109 (A) · 2516 - 732 = 1784 (H) · 10935 - 2328 = 8607 (R) · 8583 - 184 = 8399 (Y) · 10966 - 3364 = 7602 (M) · 4858 - 2972 = 1886 (L) · 5586 - 4260 = 1326 (E) · 7160 - 3629 = 3531 (O)
Clue 4 (Multiplication facts (1-12)): "GLOWING GOLDEN GRASS FELL ON THE FLOOR"
7 × 2 = 14 (G) · 5 × 7 = 35 (W) · 9 × 8 = 72 (L) · 11 × 6 = 66 (E) · 7 × 7 = 49 (O) · 7 × 8 = 56 (F) · 5 × 12 = 60 (I) · 10 × 7 = 70 (S) · 6 × 5 = 30 (A) · 9 × 9 = 81 (R) · 3 × 5 = 15 (N) · 11 × 11 = 121 (H) · 12 × 12 = 144 (T) · 2 × 2 = 4 (D)
Clue 5 (Division facts (1-12)): surviving statement (box 1) → Andrina
63 ÷ 7 = 9 · 70 ÷ 10 = 7 · 72 ÷ 6 = 12 · 50 ÷ 10 = 5 · 16 ÷ 2 = 8 · 120 ÷ 12 = 10 · 121 ÷ 11 = 11 · 6 ÷ 1 = 6 · 36 ÷ 12 = 3 · 12 ÷ 3 = 4 · 10 ÷ 5 = 2

About this mystery

Grade level: Grade 4 math
Math topics: Rounding, Addition, Subtraction, Multiplication, Division
Reading level: grades 3-4
Theme: The Case of the Missing Pearl — set in the underwater city of Pearl Cove
Format: Interactive online & printable worksheet with answer key
Solution: One unique, verified culprit among 21 suspects

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