🌊 Mermaids, prime and compositGrade 5Reading: grades 3-4Fractions of a numberOrder of operationsMultiplicationRoundingDivision
The Case of the Missing Prime Pearl
Someone snuck into the Royal Coral Vault and stole the ancient Prime Pearl! The Pearl Keeper needs your detective skills to clear the innocent mermaids and find the sneaky 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 | Main Skill | Special Gem | Dominant Hand | Hair Color | Silly Weakness |
|---|---|---|---|---|---|
| Sedna | bubble shield | prime crystal | left handed | royal purple | bright light |
| Breeze | bubble shield | prime crystal | left handed | royal purple | loud music |
| Callista | bubble shield | kelp badge | right handed | royal purple | bright light |
| Marina | shell armor | tidal rune | right handed | neon pink | loud music |
| Kai | echo siren | pearl gem | right handed | sea green | sweet fruit |
| Shelly | current glide | star stone | left handed | neon pink | bright light |
| Cascade | shell armor | star stone | right handed | neon pink | loud music |
| Ariel | current glide | star stone | right handed | royal purple | loud music |
| Triton | bubble shield | star stone | right handed | neon pink | bright light |
| Finn | wave blast | pearl gem | right handed | neon pink | loud music |
| Mako | bubble shield | tidal rune | right handed | neon pink | loud music |
| Nerida | wave blast | kelp badge | right handed | sea green | loud music |
| Pearl | shell armor | kelp badge | left handed | neon pink | loud music |
| Kelpie | shell armor | kelp badge | left handed | neon pink | sweet fruit |
| Caspian | current glide | tidal rune | left handed | neon pink | sweet fruit |
| Aquata | current glide | star stone | left handed | neon pink | loud music |
| Delphine | current glide | pearl gem | left handed | royal purple | bright light |
| Coralia | wave blast | star stone | right handed | sea green | loud music |
| Thalassa | wave blast | kelp badge | right handed | neon pink | loud music |
| Glaucus | bubble shield | prime crystal | right handed | sea green | loud music |
| Oceanus | bubble shield | pearl gem | right handed | royal purple | loud music |
Clue 1
Fractions of a number
Marina checked the fraction of pearl clam beds opened by the reef bandit.
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
22
34
5
29
39
27
27
10
39
16
33
31
5
9
16
31
T
22
21
9
5
28
5
10
36
27
11
5
38
1/6 of 132 =T
4/5 of 20 =N
4/10 of 70 =P
5/8 of 16 =A
1/4 of 136 =H
1/5 of 135 =L
2/4 of 58 =V
2/10 of 155 =O
1/8 of 40 =E
4/8 of 22 =G
1/3 of 27 =S
2/6 of 63 =U
1/4 of 144 =R
4/8 of 76 =M
3/5 of 65 =I
2/6 of 99 =D
0/16 letters found
Clue 2
Order of operations
The underwater sonar decoded a multi step rule to track the sea trail.
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
24
41
52
34
63
T
24
15
52
43
43
43
44
34
44
42
63
53
41
T
24
41
44
15
20
52
20
62
52
42
62
44
63
20
8 + 8 × 2 =T
29 + 3 × 4 =H
26 + 2 × 9 =A
5 × 7 - 1 =W
4 × 11 - 2 =R
3 + 4 × 3 =N
31 + 4 × 3 =S
42 + 5 × 4 =M
23 + 6 × 5 =G
42 + 2 × 5 =E
51 + 2 × 6 =I
5 + 5 × 3 =D
0/12 letters found
Clue 3
Multiplication facts (1-12)
Detectives counted equal rows of glow sponges along the reef wall.
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
80
77
96
56
120
42
42
54
120
64
121
42
96
45
121
35
14
110
42
14
90
45
110
90
48
120
21
8 × 10 =T
11 × 7 =H
11 × 11 =F
11 × 10 =M
2 × 7 =O
9 × 6 =A
10 × 12 =I
7 × 5 =R
8 × 12 =E
8 × 7 =V
7 × 3 =C
7 × 6 =L
12 × 4 =S
9 × 10 =U
9 × 5 =D
8 × 8 =N
0/16 letters found
Clue 4
Rounding
The trench radar only showed rounded depth measurements for the escape pod.
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
370
230
2300
300
70
2300
430
2300
230
20
4300
1700
1100
430
110
230
20
1100
130
300
T
370
130
20
430
4300
300
Round 369 to the nearest tenT
Round 106 to the nearest tenK
Round 273 to the nearest hundredS
Round 1,140 to the nearest hundredI
Round 131 to the nearest tenR
Round 70 to the nearest tenC
Round 1,663 to the nearest hundredP
Round 21 to the nearest tenA
Round 429 to the nearest tenN
Round 4,289 to the nearest hundredD
Round 2,272 to the nearest hundredE
Round 231 to the nearest tenH
0/12 letters found
Clue 5
Division facts (1-12) — the last clue
The mermaid guards divided the recovered shell tokens equally among teams.
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
77 ÷ 11 = ?
25 ÷ 5 = ?
40 ÷ 5 = ?
132 ÷ 11 = ?
70 ÷ 7 = ?
9 ÷ 3 = ?
24 ÷ 6 = ?
54 ÷ 9 = ?
8 ÷ 4 = ?
77 ÷ 7 = ?
10 ÷ 10 = ?
Step 2 — cross out the sentence with each answer
1.The villain surfed a current, then tangled a kelp badge.
2.The villain blew giant bubbles, then tangled a kelp badge.
3.The villain blew giant bubbles, then shattered a star stone.
4.The villain created a wave, then lost a pearl gem.
5.The villain created a wave, then tangled a kelp badge.
6.The villain surfed a current, then lost a pearl gem.
7.The villain swam away fast, then left a tidal rune.
8.The villain hid in coral, then shattered a star stone.
9.The villain hid in coral, then left a tidal rune.
10.The villain created a wave, then left a tidal rune.
11.The villain surfed a current, then shattered a star stone.
12.The villain blew giant bubbles, then dropped a prime crystal.
Solve it
Name the culprit
Choose the one suspect left standing.
Answer Key — The Case of the Missing Prime Pearl
Culprit: Marina (shell armor · tidal rune · right handed · neon pink · loud music)
- Clue 1 (Fractions of a number): "THE VILLAIN DOES NOT USE PEARL GEM"1/6 of 132 = 22 (T) · 4/5 of 20 = 16 (N) · 4/10 of 70 = 28 (P) · 5/8 of 16 = 10 (A) · 1/4 of 136 = 34 (H) · 1/5 of 135 = 27 (L) · 2/4 of 58 = 29 (V) · 2/10 of 155 = 31 (O) · 1/8 of 40 = 5 (E) · 4/8 of 22 = 11 (G) · 1/3 of 27 = 9 (S) · 2/6 of 63 = 21 (U) · 1/4 of 144 = 36 (R) · 4/8 of 76 = 38 (M) · 3/5 of 65 = 39 (I) · 2/6 of 99 = 33 (D)
- Clue 2 (Order of operations): "THE WITNESS SAW A RIGHT HANDED MERMAID"8 + 8 × 2 = 24 (T) · 29 + 3 × 4 = 41 (H) · 26 + 2 × 9 = 44 (A) · 5 × 7 - 1 = 34 (W) · 4 × 11 - 2 = 42 (R) · 3 + 4 × 3 = 15 (N) · 31 + 4 × 3 = 43 (S) · 42 + 5 × 4 = 62 (M) · 23 + 6 × 5 = 53 (G) · 42 + 2 × 5 = 52 (E) · 51 + 2 × 6 = 63 (I) · 5 + 5 × 3 = 20 (D)
- Clue 3 (Multiplication facts (1-12)): "THE VILLAIN FLED FROM LOUD MUSIC"8 × 10 = 80 (T) · 11 × 7 = 77 (H) · 11 × 11 = 121 (F) · 11 × 10 = 110 (M) · 2 × 7 = 14 (O) · 9 × 6 = 54 (A) · 10 × 12 = 120 (I) · 7 × 5 = 35 (R) · 8 × 12 = 96 (E) · 8 × 7 = 56 (V) · 7 × 3 = 21 (C) · 7 × 6 = 42 (L) · 12 × 4 = 48 (S) · 9 × 10 = 90 (U) · 9 × 5 = 45 (D) · 8 × 8 = 64 (N)
- Clue 4 (Rounding): "THE SCENE HAD PINK HAIR STRANDS"Round 369 to the nearest ten = 370 (T) · Round 106 to the nearest ten = 110 (K) · Round 273 to the nearest hundred = 300 (S) · Round 1,140 to the nearest hundred = 1100 (I) · Round 131 to the nearest ten = 130 (R) · Round 70 to the nearest ten = 70 (C) · Round 1,663 to the nearest hundred = 1700 (P) · Round 21 to the nearest ten = 20 (A) · Round 429 to the nearest ten = 430 (N) · Round 4,289 to the nearest hundred = 4300 (D) · Round 2,272 to the nearest hundred = 2300 (E) · Round 231 to the nearest ten = 230 (H)
- Clue 5 (Division facts (1-12)): surviving statement (box 9) → Marina77 ÷ 11 = 7 · 25 ÷ 5 = 5 · 40 ÷ 5 = 8 · 132 ÷ 11 = 12 · 70 ÷ 7 = 10 · 9 ÷ 3 = 3 · 24 ÷ 6 = 4 · 54 ÷ 9 = 6 · 8 ÷ 4 = 2 · 77 ÷ 7 = 11 · 10 ÷ 10 = 1
About this mystery
- Grade level
- Grade 5 math
- Math topics
- Fractions of a number, Order of operations, Multiplication, Rounding, Division
- Reading level
- grades 3-4
- Theme
- The Case of the Missing Prime Pearl — set in Coral Cavern Reef
- Format
- Interactive online & printable worksheet with answer key
- Solution
- One unique, verified culprit among 21 suspects