🌊 MermaidsGrade 5Reading: grades 5-6Skip countingRoundingWord problemsMulti-step word problemsMissing addends
The Mystery of the Sunken Pearl
Someone snuck into the royal sea vault of Coral Haven Reef and snatched the Glowing Sun Pearl! The High Keeper needs your detective skills to decipher ocean clues and unmask the culprit before they swim away into the deep abyss.
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 | Tail Magic | Special Gear | Accessory | Hair Color | Distraction |
|---|---|---|---|---|---|
| Harbor Ray | Tide Summoning | Speed Fins | Pearl Tiara | Seafoam Green | Sea Urchin Dust |
| Marina Wave | Coral Carving | Dolphin Whistle | Kelp Ribbon | Deep Ocean Blue | Bright Sea Flare |
| Coral Seaforth | Siren Singing | Deep Sight Scope | Pearl Tiara | Deep Ocean Blue | Sea Urchin Dust |
| Pearl Waters | Siren Singing | Speed Fins | Pearl Tiara | Coral Pink | Soft Bell Chime |
| Nerida Shell | Wave Blast | Shell Shield | Pearl Tiara | Coral Pink | Sea Urchin Dust |
| Delphine Blue | Wave Blast | Dolphin Whistle | Pearl Tiara | Seafoam Green | Sea Urchin Dust |
| Thalassa Foam | Siren Singing | Speed Fins | Pearl Tiara | Seafoam Green | Bright Sea Flare |
| Waverly Blue | Whirlpool Spin | Shell Shield | Kelp Ribbon | Seafoam Green | Sea Urchin Dust |
| Aquata Gloss | Tide Summoning | Pearl Lantern | Pearl Tiara | Seafoam Green | Sea Urchin Dust |
| Triton Reed | Siren Singing | Dolphin Whistle | Pearl Tiara | Deep Ocean Blue | Sea Urchin Dust |
| Coralina Star | Wave Blast | Speed Fins | Kelp Ribbon | Deep Ocean Blue | Sea Urchin Dust |
| Coralie Coast | Coral Carving | Deep Sight Scope | Kelp Ribbon | Coral Pink | Sea Urchin Dust |
| Sandy Reef | Tide Summoning | Deep Sight Scope | Kelp Ribbon | Deep Ocean Blue | Sea Urchin Dust |
| Caspian Drift | Coral Carving | Speed Fins | Kelp Ribbon | Deep Ocean Blue | Bright Sea Flare |
| Cleo Glint | Wave Blast | Pearl Lantern | Pearl Tiara | Seafoam Green | Sea Urchin Dust |
| Kai Current | Siren Singing | Speed Fins | Pearl Tiara | Seafoam Green | Sea Urchin Dust |
| Tarni Mist | Siren Singing | Deep Sight Scope | Kelp Ribbon | Seafoam Green | Soft Bell Chime |
| Finneas Tide | Wave Blast | Speed Fins | Pearl Tiara | Seafoam Green | Bright Sea Flare |
| Nereus Depth | Wave Blast | Pearl Lantern | Pearl Tiara | Coral Pink | Bright Sea Flare |
| Brooke Splash | Siren Singing | Speed Fins | Pearl Tiara | Coral Pink | Bright Sea Flare |
| Mako Waters | Coral Carving | Speed Fins | Pearl Tiara | Deep Ocean Blue | Sea Urchin Dust |
Clue 1
Skip counting
To track the culprit's swimming trail, follow the glowing jellyfish along the reef floor by counting in equal leaps to decode the 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.
T
120
40
130
80
30
70
70
8
30
39
60
12
130
10
39
12
T
120
110
10
130
8
60
12
70
9
40
30
39
15
40
30
10
T
120
70
130
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, ___, 130, 140T
Skip-count by 2s. Fill the blank: 2, 4, 6, ___, 10, 12A
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, ___, 12, 14S
Skip-count by 5s. Fill the blank: 5, 10, ___, 20, 25W
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, ___, 90, 100V
Skip-count by 3s. Fill the blank: 3, 6, ___, 12, 15P
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, ___, 80, 90L
Skip-count by 10s. Fill the blank: 10, 20, 30, ___, 50, 60H
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, ___, 70, 80D
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, ___, 120, 130U
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, ___, 42, 45N
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, ___, 35, 40I
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, ___, 140, 150E
Skip-count by 3s. Fill the blank: 3, 6, 9, ___, 15, 18O
0/14 letters found
Clue 2
Rounding
The vault pressure gauge only displays estimated depth values. Round the numbers to unlock the next encoded message.
Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.
A
430
3700
30
A
430
290
900
300
1300
A
430
290
A
430
370
A
430
9000
200
170
90
1700
230
230
290
170
3700
3700
30
230
A
430
300
300
20
30
130
A
430
90
900
300
Round 433 to the nearest tenA
Round 18 to the nearest tenH
Round 88 to the nearest tenU
Round 165 to the nearest hundredF
Round 293 to the nearest tenR
Round 172 to the nearest tenO
Round 230 to the nearest tenD
Round 28 to the nearest tenE
Round 366 to the nearest tenW
Round 8,952 to the nearest thousandS
Round 3,708 to the nearest hundredP
Round 302 to the nearest hundredT
Round 1,671 to the nearest hundredN
Round 1,316 to the nearest hundredI
Round 879 to the nearest hundredL
Round 133 to the nearest tenV
0/16 letters found
Clue 3
Word problems
The Tide Scout calculates the damaged shell lockets found along the reef wall to discover new evidence.
Solve each problem to learn its letter, then write the letters in the boxes to fill in the missing word.
Someonescaredthevillainoffwith .
S
76
80
17
65
37
98
51
I
N
D
65
S
76
T
There were 81 starfish tokens. 5 were used up. How many starfish tokens are left?S
There were 46 sea glass beads. 29 were used up. How many sea glass beads are left?A
There were 70 sea glass beads. 5 were used up. How many sea glass beads are left?U
Tide Scout found 18 starfish tokens yesterday and 19 more today. How many starfish tokens in all?R
Tide Scout lined up 10 rows of 8 starfish tokens. How many starfish tokens in all?E
There were 84 kelp rolls. 33 were used up. How many kelp rolls are left?H
Tide Scout found 37 kelp rolls yesterday and 61 more today. How many kelp rolls in all?C
0/7 letters found
Clue 4
Multi-step word problems
Calculating how many glowing beads were lost requires adding the original stash and subtracting the dropped loot.
Solve each problem to learn its letter, then write the letters in the boxes to fill in the missing word.
Astrandof hairturnedupatthescene.
S
62
56
48
36
14
48
7
27
R
56
56
N
There were 193 kelp rolls in all. 3 Ocean Guard used 23 kelp rolls each. The other 2 Ocean Guard shared the rest equally. How many kelp rolls did each of the other Ocean Guard get?S
Tide Scout collected 9 starfish tokens in the morning and 5 starfish tokens in the afternoon, then split them equally among 2 Ocean Guard. How many starfish tokens did each get?M
Tide Scout earned 6 sea glass beads in each of 4 rounds, plus 42 bonus sea glass beads. Then 10 sea glass beads were lost. How many sea glass beads are left?E
Tide Scout earned 3 polished shells in each of 6 rounds, plus 30 bonus polished shells. Then 12 polished shells were lost. How many polished shells are left?F
Tide Scout collected 125 sea glass beads in the morning and 163 sea glass beads in the afternoon, then split them equally among 6 Ocean Guard. How many sea glass beads did each get?A
There were 71 sea glass beads in all. 1 sea glass beads were set aside. The rest were shared equally among 5 Ocean Guard. How many sea glass beads did each get?O
Tide Scout collected 102 polished shells in the morning and 60 polished shells in the afternoon, then split them equally among 6 Ocean Guard. How many polished shells did each get?G
0/7 letters found
Clue 5
Missing addends — the last clue
The Ocean Guard ledger shows incomplete totals. Fill in the missing amounts to finish the vault report.
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
17 + ___ = 20
36 + ___ = 48
7 + ___ = 15
24 + ___ = 28
39 + ___ = 44
24 + ___ = 31
30 + ___ = 39
19 + ___ = 25
24 + ___ = 35
38 + ___ = 40
7 + ___ = 8
Step 2 — cross out the sentence with each answer
1.The villain carved through hard branch coral, then called wild sea creatures with a dolphin whistle.
2.The villain carved through hard branch coral, then scouted the secret exit with a deep sight scope.
3.The villain sang a hypnotic siren song, then darted away fast using speed fins.
4.The villain summoned a strong ocean tide, then called wild sea creatures with a dolphin whistle.
5.The villain spun a dangerous swirling whirlpool, then darted away fast using speed fins.
6.The villain sang a hypnotic siren song, then lit up the dark vault with a pearl lantern.
7.The villain blasted a powerful water wave, then blocked the guards with a heavy shell shield.
8.The villain summoned a strong ocean tide, then darted away fast using speed fins.
9.The villain carved through hard branch coral, then blocked the guards with a heavy shell shield.
10.The villain summoned a strong ocean tide, then lit up the dark vault with a pearl lantern.
11.The villain carved through hard branch coral, then darted away fast using speed fins.
12.The villain blasted a powerful water wave, then lit up the dark vault with a pearl lantern.
Solve it
Name the culprit
Choose the one suspect left standing.
Answer Key — The Mystery of the Sunken Pearl
Culprit: Aquata Gloss (Tide Summoning · Pearl Lantern · Pearl Tiara · Seafoam Green · Sea Urchin Dust)
- Clue 1 (Skip counting): "THE VILLAIN DOES NOT USE A DOLPHIN WHISTLE"Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, ___, 130, 140 = 120 (T) · Skip-count by 2s. Fill the blank: 2, 4, 6, ___, 10, 12 = 8 (A) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, ___, 12, 14 = 10 (S) · Skip-count by 5s. Fill the blank: 5, 10, ___, 20, 25 = 15 (W) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, ___, 90, 100 = 80 (V) · Skip-count by 3s. Fill the blank: 3, 6, ___, 12, 15 = 9 (P) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, ___, 80, 90 = 70 (L) · Skip-count by 10s. Fill the blank: 10, 20, 30, ___, 50, 60 = 40 (H) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, ___, 70, 80 = 60 (D) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, ___, 120, 130 = 110 (U) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, ___, 42, 45 = 39 (N) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, ___, 35, 40 = 30 (I) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, ___, 140, 150 = 130 (E) · Skip-count by 3s. Fill the blank: 3, 6, 9, ___, 15, 18 = 12 (O)
- Clue 2 (Rounding): "A PEARL TIARA WAS FOUND DROPPED AT THE VAULT"Round 433 to the nearest ten = 430 (A) · Round 18 to the nearest ten = 20 (H) · Round 88 to the nearest ten = 90 (U) · Round 165 to the nearest hundred = 200 (F) · Round 293 to the nearest ten = 290 (R) · Round 172 to the nearest ten = 170 (O) · Round 230 to the nearest ten = 230 (D) · Round 28 to the nearest ten = 30 (E) · Round 366 to the nearest ten = 370 (W) · Round 8,952 to the nearest thousand = 9000 (S) · Round 3,708 to the nearest hundred = 3700 (P) · Round 302 to the nearest hundred = 300 (T) · Round 1,671 to the nearest hundred = 1700 (N) · Round 1,316 to the nearest hundred = 1300 (I) · Round 879 to the nearest hundred = 900 (L) · Round 133 to the nearest ten = 130 (V)
- Clue 3 (Word problems): "SEA URCHIN DUST"There were 81 starfish tokens. 5 were used up. How many starfish tokens are left? = 76 (S) · There were 46 sea glass beads. 29 were used up. How many sea glass beads are left? = 17 (A) · There were 70 sea glass beads. 5 were used up. How many sea glass beads are left? = 65 (U) · Tide Scout found 18 starfish tokens yesterday and 19 more today. How many starfish tokens in all? = 37 (R) · Tide Scout lined up 10 rows of 8 starfish tokens. How many starfish tokens in all? = 80 (E) · There were 84 kelp rolls. 33 were used up. How many kelp rolls are left? = 51 (H) · Tide Scout found 37 kelp rolls yesterday and 61 more today. How many kelp rolls in all? = 98 (C)
- Clue 4 (Multi-step word problems): "SEAFOAM GREEN"There were 193 kelp rolls in all. 3 Ocean Guard used 23 kelp rolls each. The other 2 Ocean Guard shared the rest equally. How many kelp rolls did each of the other Ocean Guard get? = 62 (S) · Tide Scout collected 9 starfish tokens in the morning and 5 starfish tokens in the afternoon, then split them equally among 2 Ocean Guard. How many starfish tokens did each get? = 7 (M) · Tide Scout earned 6 sea glass beads in each of 4 rounds, plus 42 bonus sea glass beads. Then 10 sea glass beads were lost. How many sea glass beads are left? = 56 (E) · Tide Scout earned 3 polished shells in each of 6 rounds, plus 30 bonus polished shells. Then 12 polished shells were lost. How many polished shells are left? = 36 (F) · Tide Scout collected 125 sea glass beads in the morning and 163 sea glass beads in the afternoon, then split them equally among 6 Ocean Guard. How many sea glass beads did each get? = 48 (A) · There were 71 sea glass beads in all. 1 sea glass beads were set aside. The rest were shared equally among 5 Ocean Guard. How many sea glass beads did each get? = 14 (O) · Tide Scout collected 102 polished shells in the morning and 60 polished shells in the afternoon, then split them equally among 6 Ocean Guard. How many polished shells did each get? = 27 (G)
- Clue 5 (Missing addends): surviving statement (box 10) → Aquata Gloss17 + ___ = 20 = 3 · 36 + ___ = 48 = 12 · 7 + ___ = 15 = 8 · 24 + ___ = 28 = 4 · 39 + ___ = 44 = 5 · 24 + ___ = 31 = 7 · 30 + ___ = 39 = 9 · 19 + ___ = 25 = 6 · 24 + ___ = 35 = 11 · 38 + ___ = 40 = 2 · 7 + ___ = 8 = 1
About this mystery
- Grade level
- Grade 5 math
- Math topics
- Skip counting, Rounding, Word problems, Multi-step word problems, Missing addends
- Reading level
- grades 5-6
- Theme
- The Mystery of the Sunken Pearl — set in Coral Haven Reef
- Format
- Interactive online & printable worksheet with answer key
- Solution
- One unique, verified culprit among 21 suspects