🌊 MermaidsGrade 2Reading: grades 1-2AdditionSubtractionSkip countingPlace valueMissing addends
The Mystery of the Coral Crown
Someone took the shiny Coral Crown from the Pearl Keeper! The deep blue sea needs your help. We must find the tide thief before the big ocean party 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 | Swim Magic | Sea Companion | Swim Style | Shell Crown | Aura Weakness |
|---|---|---|---|---|---|
| Marina | Wave speed | Octopus scout | Left-handed swimmer | Pink kelp bows | Bright warm sand |
| Ariel | Tide jump | Seahorse pal | Right-handed swimmer | Starfish clips | Bright warm sand |
| River | Wave speed | Dolphin guide | Right-handed swimmer | Pink kelp bows | Noisy clam snaps |
| Melody | Whirlpool spin | Crab helper | Left-handed swimmer | Pink kelp bows | Tickly sea grass |
| Cleo | Whirlpool spin | Crab helper | Right-handed swimmer | Starfish clips | Noisy clam snaps |
| Gemma | Wave speed | Turtle friend | Right-handed swimmer | Starfish clips | Tickly sea grass |
| Brooke | Current glide | Dolphin guide | Right-handed swimmer | Starfish clips | Bright warm sand |
| Aqua | Bubble shield | Crab helper | Right-handed swimmer | Pink kelp bows | Noisy clam snaps |
| Opal | Current glide | Crab helper | Right-handed swimmer | Starfish clips | Bright warm sand |
| Blue | Wave speed | Crab helper | Right-handed swimmer | Starfish clips | Noisy clam snaps |
| Nerida | Whirlpool spin | Dolphin guide | Left-handed swimmer | Starfish clips | Noisy clam snaps |
| Shelly | Whirlpool spin | Octopus scout | Left-handed swimmer | Purple sea lace | Noisy clam snaps |
| Star | Whirlpool spin | Octopus scout | Right-handed swimmer | Starfish clips | Noisy clam snaps |
| Delta | Tide jump | Crab helper | Right-handed swimmer | Starfish clips | Tickly sea grass |
| Wave | Current glide | Turtle friend | Left-handed swimmer | Starfish clips | Tickly sea grass |
| Lana | Bubble shield | Dolphin guide | Left-handed swimmer | Starfish clips | Tickly sea grass |
| Coral | Bubble shield | Seahorse pal | Right-handed swimmer | Starfish clips | Tickly sea grass |
| Misty | Current glide | Turtle friend | Right-handed swimmer | Starfish clips | Noisy clam snaps |
| Talia | Tide jump | Turtle friend | Right-handed swimmer | Pink kelp bows | Tickly sea grass |
| Pearl | Whirlpool spin | Octopus scout | Right-handed swimmer | Pink kelp bows | Bright warm sand |
| Sunny | Current glide | Crab helper | Right-handed swimmer | Starfish clips | Noisy clam snaps |
Clue 1
Addition
We found a pile of shiny pearls dropped on the sea floor. Let us add them all up to see how many the thief dropped.
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
87
50
91
T
87
50
34
91
67
84
63
91
21
75
63
T
87
50
52
59
91
52
75
63
48
T
87
63
24
40
21
21
48
63
40
T
87
55 + 32 =T
28 + 12 =U
27 + 48 =N
22 + 12 =I
28 + 31 =V
50 + 34 =D
33 + 58 =E
24 + 24 =C
7 + 14 =S
13 + 11 =P
35 + 17 =A
25 + 42 =F
20 + 30 =H
30 + 33 =O
0/14 letters found
Clue 2
Subtraction
The thief fed some fish from a basket to make them stay still. Subtract the fish that are left to see how many were eaten.
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
77
45
43
T
77
45
87
43
40
71
86
87
32
71
32
53
87
55
66
26
86
87
T
77
45
T
77
45
43
88
87
11
45
T
77
45
53
55
21
84 - 7 =T
61 - 21 =F
65 - 33 =M
22 - 11 =G
82 - 39 =E
83 - 12 =S
94 - 6 =R
29 - 8 =D
85 - 19 =L
65 - 20 =H
87 - 1 =W
86 - 33 =A
65 - 39 =Y
95 - 8 =I
62 - 7 =N
0/15 letters found
Clue 3
Skip counting
Look at these starfish tracks in the sand. They form groups of five. Let us skip count the legs to find the path.
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
110
22
55
T
110
22
39
55
130
16
30
50
55
100
20
T
110
22
55
39
100
55
80
100
20
9
55
80
100
16
65
80
14
20
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, ___, 120, 130T
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, ___, 140, 150F
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, ___, 110, 120R
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, ___, 16, 18M
Skip-count by 10s. Fill the blank: 10, 20, ___, 40, 50O
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, ___, 24, 26H
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, ___, 42, 45I
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, ___, 55, 60V
Skip-count by 3s. Fill the blank: 3, 6, ___, 12, 15N
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, ___, 18, 20C
Skip-count by 5s. Fill the blank: 5, 10, 15, ___, 25, 30S
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, ___, 90, 100A
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, ___, 70, 75L
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, ___, 60, 65E
0/14 letters found
Clue 4
Place value
A secret box has a lock with tens and ones. Count the big clams and little shells to find the code.
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
73
47
29
A
73
82
44
18
47
40
25
46
18
86
83
A
73
47
43
82
92
86
86
99
43
18
74
29
40
99
52
31
43
What number has 7 tens and 3 ones?A
What number has 5 tens and 2 ones?M
What number has 7 tens and 4 ones?N
What number has 4 tens and 4 ones?F
What number has 1 ten and 8 ones?I
What number has 9 tens and 9 ones?E
What number has 3 tens and 1 one?U
What number has 4 tens and 3 ones?D
What number has 2 tens and 5 ones?C
What number has 8 tens and 6 ones?P
What number has 4 tens and 7 ones?S
What number has 4 tens and 6 ones?L
What number has 2 tens and 9 ones?T
What number has 8 tens and 2 ones?R
What number has 4 tens and 0 ones?H
What number has 8 tens and 3 ones?W
What number has 9 tens and 2 ones?O
0/17 letters found
Clue 5
Missing addends — the last clue
The thief needs ten glowing jellyfish to light the dark cave. They only have six. Find how many more they must catch.
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
9 + ___ = 16
6 + ___ = 17
2 + ___ = 14
9 + ___ = 15
10 + ___ = 20
6 + ___ = 11
6 + ___ = 7
9 + ___ = 18
4 + ___ = 8
10 + ___ = 12
9 + ___ = 17
Step 2 — cross out the sentence with each answer
1.The villain creates a whirlpool spin, then whistles for a seahorse pal.
2.The villain rides the fast wave speed, then signals an octopus scout.
3.The villain rides the fast wave speed, then asks a crab helper to dig a hole.
4.The villain slides on the current glide, then signals an octopus scout.
5.The villain swims through the bubble shield, then rides a turtle friend away.
6.The villain performs a high tide jump, then calls a dolphin guide to escape.
7.The villain slides on the current glide, then rides a turtle friend away.
8.The villain slides on the current glide, then whistles for a seahorse pal.
9.The villain swims through the bubble shield, then calls a dolphin guide to escape.
10.The villain creates a whirlpool spin, then calls a dolphin guide to escape.
11.The villain slides on the current glide, then asks a crab helper to dig a hole.
12.The villain creates a whirlpool spin, then asks a crab helper to dig a hole.
Solve it
Name the culprit
Choose the one suspect left standing.
Answer Key — The Mystery of the Coral Crown
Culprit: Blue (Wave speed · Crab helper · Right-handed swimmer · Starfish clips · Noisy clam snaps)
- Clue 1 (Addition): "THE THIEF DOES NOT HAVE AN OCTOPUS SCOUT"55 + 32 = 87 (T) · 28 + 12 = 40 (U) · 27 + 48 = 75 (N) · 22 + 12 = 34 (I) · 28 + 31 = 59 (V) · 50 + 34 = 84 (D) · 33 + 58 = 91 (E) · 24 + 24 = 48 (C) · 7 + 14 = 21 (S) · 13 + 11 = 24 (P) · 35 + 17 = 52 (A) · 25 + 42 = 67 (F) · 20 + 30 = 50 (H) · 30 + 33 = 63 (O)
- Clue 2 (Subtraction): "THE THIEF SWIMS MAINLY WITH THE RIGHT HAND"84 - 7 = 77 (T) · 61 - 21 = 40 (F) · 65 - 33 = 32 (M) · 22 - 11 = 11 (G) · 82 - 39 = 43 (E) · 83 - 12 = 71 (S) · 94 - 6 = 88 (R) · 29 - 8 = 21 (D) · 85 - 19 = 66 (L) · 65 - 20 = 45 (H) · 87 - 1 = 86 (W) · 86 - 33 = 53 (A) · 65 - 39 = 26 (Y) · 95 - 8 = 87 (I) · 62 - 7 = 55 (N)
- Clue 3 (Skip counting): "THE THIEF COVERS THEIR EARS NEAR CLAMS"Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, ___, 120, 130 = 110 (T) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, ___, 140, 150 = 130 (F) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, ___, 110, 120 = 100 (R) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, ___, 16, 18 = 14 (M) · Skip-count by 10s. Fill the blank: 10, 20, ___, 40, 50 = 30 (O) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, ___, 24, 26 = 22 (H) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, ___, 42, 45 = 39 (I) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, ___, 55, 60 = 50 (V) · Skip-count by 3s. Fill the blank: 3, 6, ___, 12, 15 = 9 (N) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, ___, 18, 20 = 16 (C) · Skip-count by 5s. Fill the blank: 5, 10, 15, ___, 25, 30 = 20 (S) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, ___, 90, 100 = 80 (A) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, ___, 70, 75 = 65 (L) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, ___, 60, 65 = 55 (E)
- Clue 4 (Place value): "A STARFISH CLIP WAS DROPPED IN THE MUD"What number has 7 tens and 3 ones? = 73 (A) · What number has 5 tens and 2 ones? = 52 (M) · What number has 7 tens and 4 ones? = 74 (N) · What number has 4 tens and 4 ones? = 44 (F) · What number has 1 ten and 8 ones? = 18 (I) · What number has 9 tens and 9 ones? = 99 (E) · What number has 3 tens and 1 one? = 31 (U) · What number has 4 tens and 3 ones? = 43 (D) · What number has 2 tens and 5 ones? = 25 (C) · What number has 8 tens and 6 ones? = 86 (P) · What number has 4 tens and 7 ones? = 47 (S) · What number has 4 tens and 6 ones? = 46 (L) · What number has 2 tens and 9 ones? = 29 (T) · What number has 8 tens and 2 ones? = 82 (R) · What number has 4 tens and 0 ones? = 40 (H) · What number has 8 tens and 3 ones? = 83 (W) · What number has 9 tens and 2 ones? = 92 (O)
- Clue 5 (Missing addends): surviving statement (box 3) → Blue9 + ___ = 16 = 7 · 6 + ___ = 17 = 11 · 2 + ___ = 14 = 12 · 9 + ___ = 15 = 6 · 10 + ___ = 20 = 10 · 6 + ___ = 11 = 5 · 6 + ___ = 7 = 1 · 9 + ___ = 18 = 9 · 4 + ___ = 8 = 4 · 10 + ___ = 12 = 2 · 9 + ___ = 17 = 8
About this mystery
- Grade level
- Grade 2 math
- Math topics
- Addition, Subtraction, Skip counting, Place value, Missing addends
- Reading level
- grades 1-2
- Theme
- The Mystery of the Coral Crown — set in Coral Cove
- Format
- Interactive online & printable worksheet with answer key
- Solution
- One unique, verified culprit among 21 suspects