🌊 MermaidsGrade 6Reading: grades 5-6Place valueRoundingAdditionMultiplicationDivision
The Mystery of the Sunken Royal Trident
During the annual Sunken Coral Festival, someone snuck into the royal vault and took the Sacred Tide Trident! The Royal Reef Guard needs your detective skills to decode the underwater clues, track the traits, and catch the thief.
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 | Tide Power | Seabed Tool | Swimming Style | Hair Streak | Disliked Sound |
|---|---|---|---|---|---|
| Nerida | Current Dash | Pearl Lantern | Left Handed Swimming | Ocean Blue Hair | Bright Jelly Glow |
| Coralline | Current Dash | Shell Compass | Left Handed Swimming | Ocean Blue Hair | Loud Conch Horns |
| Finn | Current Dash | Crab Whistle | Left Handed Swimming | Ocean Blue Hair | Bright Jelly Glow |
| Azure | Current Dash | Anchor Weight | Left Handed Swimming | Coral Pink Hair | Bright Jelly Glow |
| Triton | Kelp Weaving | Sea Glass Charm | Right Handed Swimming | Coral Pink Hair | Loud Conch Horns |
| Marina | Tide Bending | Pearl Lantern | Right Handed Swimming | Coral Pink Hair | Bright Jelly Glow |
| Zephyr | Whirlpool Magic | Crab Whistle | Left Handed Swimming | Ocean Blue Hair | Tickle Sea Sponge |
| Urchin | Kelp Weaving | Anchor Weight | Right Handed Swimming | Coral Pink Hair | Bright Jelly Glow |
| Cove | Current Dash | Shell Compass | Left Handed Swimming | Ocean Blue Hair | Bright Jelly Glow |
| Nixie | Whirlpool Magic | Crab Whistle | Right Handed Swimming | Ocean Blue Hair | Bright Jelly Glow |
| Caspian | Siren Harmony | Crab Whistle | Left Handed Swimming | Coral Pink Hair | Loud Conch Horns |
| Pearl | Current Dash | Pearl Lantern | Left Handed Swimming | Coral Pink Hair | Bright Jelly Glow |
| Reef | Siren Harmony | Sea Glass Charm | Right Handed Swimming | Ocean Blue Hair | Loud Conch Horns |
| Mako | Tide Bending | Crab Whistle | Left Handed Swimming | Ocean Blue Hair | Loud Conch Horns |
| Briny | Whirlpool Magic | Anchor Weight | Right Handed Swimming | Coral Pink Hair | Tickle Sea Sponge |
| Oceania | Whirlpool Magic | Sea Glass Charm | Right Handed Swimming | Kelp Green Hair | Bright Jelly Glow |
| Waverly | Whirlpool Magic | Pearl Lantern | Right Handed Swimming | Ocean Blue Hair | Loud Conch Horns |
| Kai | Tide Bending | Anchor Weight | Right Handed Swimming | Ocean Blue Hair | Loud Conch Horns |
| Delphina | Current Dash | Anchor Weight | Left Handed Swimming | Ocean Blue Hair | Bright Jelly Glow |
| Nerea | Kelp Weaving | Sea Glass Charm | Left Handed Swimming | Coral Pink Hair | Bright Jelly Glow |
| Thalassa | Siren Harmony | Crab Whistle | Left Handed Swimming | Ocean Blue Hair | Bright Jelly Glow |
Clue 1
Place value
You examine the sonar board where digit positions reveal a secret cipher depth.
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
9000
500
50
800
6000
70
70
30
6000
200
400
10
50
4000
200
10
T
9000
8000
4000
50
30
3000
50
30
700
70
70
30
200
T
9000
50
700
200
What is the value of the 9 in 889,811?T
What is the value of the 1 in 62,615?O
What is the value of the 5 in 276,657?E
What is the value of the 8 in 729,876?V
What is the value of the 6 in 176,207?I
What is the value of the 8 in 28,134?U
What is the value of the 7 in 31,574?L
What is the value of the 3 in 83,151?P
What is the value of the 4 in 14,675?S
What is the value of the 4 in 867,466?D
What is the value of the 7 in 81,798?R
What is the value of the 3 in 68,537?A
What is the value of the 5 in 826,584?H
What is the value of the 2 in 98,208?N
0/14 letters found
Clue 2
Rounding
The deep sea gauge only displays depth numbers rounded to the nearest hundred.
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
200
230
500
110
300
110
1700
500
7000
T
200
300
110
500
3000
4300
500
20
T
200
230
700
90
3000
500
3000
110
1100
130
30
30
130
90
50
Round 168 to the nearest hundredT
Round 324 to the nearest hundredU
Round 2,782 to the nearest thousandD
Round 22 to the nearest tenF
Round 233 to the nearest tenH
Round 4,317 to the nearest hundredL
Round 93 to the nearest tenN
Round 108 to the nearest tenS
Round 133 to the nearest tenI
Round 714 to the nearest hundredA
Round 51 to the nearest tenG
Round 6,676 to the nearest thousandC
Round 26 to the nearest tenM
Round 1,657 to the nearest hundredP
Round 462 to the nearest hundredE
Round 1,120 to the nearest hundredW
0/16 letters found
Clue 3
Addition
You tally up the glowing crystals gathered from around the sunken grotto.
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
9817
4826
6216
3999
6314
3999
3227
6216
3914
T
9817
3002
8125
8923
2680
6216
2944
8125
3988
8125
8923
4677
3999
T
9817
7828
3455
8923
3988
4826
T
9817
2753
6216
2680
2680
4653
3988
2680
8610
5735
3767 + 6050 =T
2131 + 1324 =R
2133 + 3602 =W
5348 + 3262 =O
3230 + 2986 =E
2975 + 1678 =Y
4252 + 4671 =I
1842 + 1102 =D
1429 + 2559 =G
1602 + 2312 =C
1033 + 1647 =L
1502 + 1251 =J
2555 + 1444 =S
3849 + 3979 =B
4691 + 3434 =A
1747 + 3079 =H
1280 + 1722 =F
3893 + 2421 =U
2746 + 1931 =N
1323 + 1904 =P
0/20 letters found
Clue 4
Multiplication facts (1-12)
The guard count comes from multiplying rows of clam shell vaults.
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
49
55
7
50
132
7
35
7
132
48
35
T
49
70
60
35
7
8
48
132
7
70
35
108
84
56
7
55
70
60
54
7 × 7 =T
6 × 9 =R
7 × 12 =L
12 × 9 =B
6 × 8 =O
5 × 7 =N
4 × 2 =D
8 × 7 =U
11 × 5 =H
1 × 7 =E
5 × 10 =S
5 × 12 =I
12 × 11 =C
10 × 7 =A
0/14 letters found
Clue 5
Division facts (1-12) — the last clue
To open the treasure lock you must divide the magical pearls into equal sea sacks.
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 ÷ 3 = ?
12 ÷ 1 = ?
9 ÷ 1 = ?
28 ÷ 4 = ?
60 ÷ 10 = ?
30 ÷ 10 = ?
36 ÷ 9 = ?
64 ÷ 8 = ?
14 ÷ 7 = ?
55 ÷ 11 = ?
8 ÷ 8 = ?
Step 2 — cross out the sentence with each answer
1.The villain bent the ocean tides, then dropped an anchor weight.
2.The villain summoned a whirlpool, then checked a shell compass.
3.The villain chanted siren harmonies, then checked a shell compass.
4.The villain bent the ocean tides, then lit a pearl lantern.
5.The villain chanted siren harmonies, then lit a pearl lantern.
6.The villain wove thick kelp ropes, then dropped an anchor weight.
7.The villain dashed with current speed, then flashed a sea glass charm.
8.The villain summoned a whirlpool, then flashed a sea glass charm.
9.The villain dashed with current speed, then checked a shell compass.
10.The villain dashed with current speed, then blew a crab whistle.
11.The villain chanted siren harmonies, then blew a crab whistle.
12.The villain dashed with current speed, then dropped an anchor weight.
Solve it
Name the culprit
Choose the one suspect left standing.
Answer Key — The Mystery of the Sunken Royal Trident
Culprit: Thalassa (Siren Harmony · Crab Whistle · Left Handed Swimming · Ocean Blue Hair · Bright Jelly Glow)
- Clue 1 (Place value): "THE VILLAIN DOES NOT USE A PEARL LANTERN"What is the value of the 9 in 889,811? = 9000 (T) · What is the value of the 1 in 62,615? = 10 (O) · What is the value of the 5 in 276,657? = 50 (E) · What is the value of the 8 in 729,876? = 800 (V) · What is the value of the 6 in 176,207? = 6000 (I) · What is the value of the 8 in 28,134? = 8000 (U) · What is the value of the 7 in 31,574? = 70 (L) · What is the value of the 3 in 83,151? = 3000 (P) · What is the value of the 4 in 14,675? = 4000 (S) · What is the value of the 4 in 867,466? = 400 (D) · What is the value of the 7 in 81,798? = 700 (R) · What is the value of the 3 in 68,537? = 30 (A) · What is the value of the 5 in 826,584? = 500 (H) · What is the value of the 2 in 98,208? = 200 (N)
- Clue 2 (Rounding): "THE SUSPECT USED LEFT HANDED SWIMMING"Round 168 to the nearest hundred = 200 (T) · Round 324 to the nearest hundred = 300 (U) · Round 2,782 to the nearest thousand = 3000 (D) · Round 22 to the nearest ten = 20 (F) · Round 233 to the nearest ten = 230 (H) · Round 4,317 to the nearest hundred = 4300 (L) · Round 93 to the nearest ten = 90 (N) · Round 108 to the nearest ten = 110 (S) · Round 133 to the nearest ten = 130 (I) · Round 714 to the nearest hundred = 700 (A) · Round 51 to the nearest ten = 50 (G) · Round 6,676 to the nearest thousand = 7000 (C) · Round 26 to the nearest ten = 30 (M) · Round 1,657 to the nearest hundred = 1700 (P) · Round 462 to the nearest hundred = 500 (E) · Round 1,120 to the nearest hundred = 1100 (W)
- Clue 3 (Addition): "THE SUSPECT FAILED AGAINST BRIGHT JELLY GLOW"3767 + 6050 = 9817 (T) · 2131 + 1324 = 3455 (R) · 2133 + 3602 = 5735 (W) · 5348 + 3262 = 8610 (O) · 3230 + 2986 = 6216 (E) · 2975 + 1678 = 4653 (Y) · 4252 + 4671 = 8923 (I) · 1842 + 1102 = 2944 (D) · 1429 + 2559 = 3988 (G) · 1602 + 2312 = 3914 (C) · 1033 + 1647 = 2680 (L) · 1502 + 1251 = 2753 (J) · 2555 + 1444 = 3999 (S) · 3849 + 3979 = 7828 (B) · 4691 + 3434 = 8125 (A) · 1747 + 3079 = 4826 (H) · 1280 + 1722 = 3002 (F) · 3893 + 2421 = 6314 (U) · 2746 + 1931 = 4677 (N) · 1323 + 1904 = 3227 (P)
- Clue 4 (Multiplication facts (1-12)): "THE SCENE CONTAINED OCEAN BLUE HAIR"7 × 7 = 49 (T) · 6 × 9 = 54 (R) · 7 × 12 = 84 (L) · 12 × 9 = 108 (B) · 6 × 8 = 48 (O) · 5 × 7 = 35 (N) · 4 × 2 = 8 (D) · 8 × 7 = 56 (U) · 11 × 5 = 55 (H) · 1 × 7 = 7 (E) · 5 × 10 = 50 (S) · 5 × 12 = 60 (I) · 12 × 11 = 132 (C) · 10 × 7 = 70 (A)
- Clue 5 (Division facts (1-12)): surviving statement (box 11) → Thalassa30 ÷ 3 = 10 · 12 ÷ 1 = 12 · 9 ÷ 1 = 9 · 28 ÷ 4 = 7 · 60 ÷ 10 = 6 · 30 ÷ 10 = 3 · 36 ÷ 9 = 4 · 64 ÷ 8 = 8 · 14 ÷ 7 = 2 · 55 ÷ 11 = 5 · 8 ÷ 8 = 1
About this mystery
- Grade level
- Grade 6 math
- Math topics
- Place value, Rounding, Addition, Multiplication, Division
- Reading level
- grades 5-6
- Theme
- The Mystery of the Sunken Royal Trident — set in Coral Kingdom of Shimmering Reef
- Format
- Interactive online & printable worksheet with answer key
- Solution
- One unique, verified culprit among 21 suspects