🌊 MermaidsGrade 7Reading: grades 7-9Fractions of a numberBar modelsMultiplicationIntegers
The Case of the Missing Pearl Scepter
The royal vault of Aquaria has been breached! The ancient Pearl Scepter, which keeps the tides in perfect balance, is gone. The Chief Pearl Guardian was found trapped inside a giant sea anemone, pointing toward the deep trenches. The Coral Council has summoned you to analyze the physical traces left behind and identify the rogue tide-weaver before the great oceanic storm is unleashed.
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 Power | Extra Power | Physical Tell | Hair Color | Vulnerability |
|---|---|---|---|---|---|
| Calypso | tide summoning | glowing scales | right finned drift | coral pink | citrus peel |
| Naida | tempest song | ice breath | left finned drift | abalone silver | deep sonar |
| Thallo | marine telepathy | ice breath | left finned drift | kelp green | deep sonar |
| Rikki | marine telepathy | mimicry | left finned drift | kelp green | citrus peel |
| Tritonus | coral shaping | shadow camouflage | left finned drift | coral pink | citrus peel |
| Delphine | tide summoning | shadow camouflage | right finned drift | kelp green | deep sonar |
| Coralia | tempest song | shadow camouflage | right finned drift | kelp green | warm currents |
| Oceanus | coral shaping | glowing scales | left finned drift | abalone silver | deep sonar |
| Sirena | tempest song | glowing scales | left finned drift | coral pink | citrus peel |
| Madison | hydrokinesis | glowing scales | right finned drift | abalone silver | warm currents |
| Nerida | coral shaping | ice breath | left finned drift | coral pink | warm currents |
| Emma | coral shaping | glowing scales | left finned drift | kelp green | warm currents |
| Undine | marine telepathy | glowing scales | left finned drift | abalone silver | citrus peel |
| Melusine | marine telepathy | glowing scales | right finned drift | abalone silver | warm currents |
| Cleo | hydrokinesis | glowing scales | left finned drift | coral pink | warm currents |
| Glaucus | tempest song | mimicry | left finned drift | coral pink | citrus peel |
| Chelsea | marine telepathy | mimicry | left finned drift | coral pink | citrus peel |
| Muriel | hydrokinesis | sonic click | left finned drift | coral pink | citrus peel |
| Triton | hydrokinesis | mimicry | right finned drift | abalone silver | citrus peel |
| Ariel | hydrokinesis | glowing scales | right finned drift | kelp green | citrus peel |
| Marina | tide summoning | mimicry | left finned drift | abalone silver | citrus peel |
Clue 1
Fractions of a number
We recovered a damaged manifest from the royal vault where only a fraction of the total pearl tally remains visible.
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
42
59
5
T
42
36
50
28
5
T
42
44
17
5
27
23
17
T
42
18
27
5
27
59
36
44
17
31
29
36
24
17
18
49
35
36
28
5
4/6 of 63 =T
2/6 of 84 =G
4/5 of 55 =D
1/2 of 98 =F
1/6 of 174 =C
4/10 of 90 =A
1/2 of 70 =L
1/4 of 92 =N
2/10 of 85 =O
4/6 of 36 =M
1/4 of 108 =S
1/8 of 144 =U
5/6 of 60 =R
2/8 of 20 =E
4/8 of 118 =H
1/2 of 62 =W
0/16 letters found
Clue 2
Bar model word problems
Our scouts charted the thief's escape velocity using visual grid bars to compare the speed of different ocean currents.
Draw a bar model to solve each word problem. Its answer reveals a letter — write the letters in the boxes to fill in the missing word.
Awitnesssawthevillainwas .
L
88
16
25
89
25
126
115
115
16
23
23
R
126
25
89
There were 94 sea-glass tokens in all. 6 sea-glass tokens were used. How many sea-glass tokens are left?
draw a bar model
Answer:→L
Reef-scout has 8 times as many starfish medals as a teammate. The teammate has 2 starfish medals. How many starfish medals does reef-scout have?
draw a bar model
Answer:→E
There were 120 kelp bundles in all. 31 kelp bundles were used. How many kelp bundles are left?
draw a bar model
Answer:→T
Reef-scout has 138 clam shells, packed 6 to a bag. How many bags can be filled?
draw a bar model
Answer:→D
Reef-scout shares 200 kelp bundles equally among 8 teams. How many kelp bundles does each team get?
draw a bar model
Answer:→F
One group collected 29 sea-glass tokens and another group collected 97 sea-glass tokens. How many sea-glass tokens in all?
draw a bar model
Answer:→I
There were 146 starfish medals in all. 31 starfish medals were used. How many starfish medals are left?
draw a bar model
Answer:→N
0/7 letters found
Clue 3
Multiplication facts (1-12)
Deep-sea divers discovered rows of discarded oyster shells stacked in perfect formations outside the reef.
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
27
49
1
T
27
48
60
72
1
T
27
24
1
48
42
1
63
36
63
1
48
60
8
40
T
27
T
27
1
60
33
1
45
80
63
36
3 × 9 =T
11 × 3 =L
7 × 7 =H
8 × 3 =W
12 × 4 =A
9 × 7 =N
6 × 12 =G
6 × 10 =R
10 × 8 =O
9 × 5 =M
1 × 8 =B
4 × 9 =S
10 × 4 =I
1 × 1 =E
6 × 7 =K
0/15 letters found
Clue 4
Integers
Thermometer readings from the abyssal plain show rising and falling temperatures as the thief swam past.
Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.
P
26
8
1
23
30
13
8
12
6
13
1
17
10
16
19
27
1
6
30
16
12
16
16
3
7
27
12
13
10
16 - (-10) =P
(-10) + 27 =G
7 - (-1) =I
(-13) + 36 =K
(-2) + 3 =N
(-11) + 41 =H
(-12) + 25 =A
21 - (-6) =O
(-3) + 6 =F
(-15) + 27 =R
(-4) + 10 =T
(-11) + 27 =E
4 - (-6) =L
(-8) + 15 =C
(-9) + 28 =S
0/15 letters found
Clue 5
Fractions of a number — the last clue
The local sea turtles gathered scattered prism stones, but we only have a fraction of their original hoard to study.
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
1/5 of 15 = ?
5/6 of 12 = ?
4/6 of 3 = ?
2/3 of 6 = ?
4/8 of 18 = ?
3/6 of 14 = ?
4/10 of 20 = ?
1/4 of 48 = ?
2/10 of 25 = ?
1/3 of 3 = ?
1/3 of 33 = ?
Step 2 — cross out the sentence with each answer
1.The villain commands a school of reef sharks, then freezes the surrounding warm waters.
2.The villain commands a school of reef sharks, then mimics the song of a nearby whale.
3.The villain manipulates the sea currents, then shatters the oyster shells with a click.
4.The villain manipulates the sea currents, then fades away into the deep shadows.
5.The villain summons a swirling ocean gale, then shatters the oyster shells with a click.
6.The villain summons a swirling ocean gale, then leaves a trail of luminescent bubbles.
7.The villain commands a school of reef sharks, then fades away into the deep shadows.
8.The villain grows a massive coral barrier, then shatters the oyster shells with a click.
9.The villain grows a massive coral barrier, then leaves a trail of luminescent bubbles.
10.The villain summons a swirling ocean gale, then mimics the song of a nearby whale.
11.The villain calls upon a high tidal wave, then mimics the song of a nearby whale.
12.The villain commands a school of reef sharks, then shatters the oyster shells with a click.
Solve it
Name the culprit
Choose the one suspect left standing.
Answer Key — The Case of the Missing Pearl Scepter
Culprit: Sirena (tempest song · glowing scales · left finned drift · coral pink · citrus peel)
- Clue 1 (Fractions of a number): "THE TARGET DOES NOT USE SHADOW CAMOUFLAGE"4/6 of 63 = 42 (T) · 2/6 of 84 = 28 (G) · 4/5 of 55 = 44 (D) · 1/2 of 98 = 49 (F) · 1/6 of 174 = 29 (C) · 4/10 of 90 = 36 (A) · 1/2 of 70 = 35 (L) · 1/4 of 92 = 23 (N) · 2/10 of 85 = 17 (O) · 4/6 of 36 = 24 (M) · 1/4 of 108 = 27 (S) · 1/8 of 144 = 18 (U) · 5/6 of 60 = 50 (R) · 2/8 of 20 = 5 (E) · 4/8 of 118 = 59 (H) · 1/2 of 62 = 31 (W)
- Clue 2 (Bar model word problems): "LEFT FINNED DRIFT"There were 94 sea-glass tokens in all. 6 sea-glass tokens were used. How many sea-glass tokens are left? = 88 (L) · Reef-scout has 8 times as many starfish medals as a teammate. The teammate has 2 starfish medals. How many starfish medals does reef-scout have? = 16 (E) · There were 120 kelp bundles in all. 31 kelp bundles were used. How many kelp bundles are left? = 89 (T) · Reef-scout has 138 clam shells, packed 6 to a bag. How many bags can be filled? = 23 (D) · Reef-scout shares 200 kelp bundles equally among 8 teams. How many kelp bundles does each team get? = 25 (F) · One group collected 29 sea-glass tokens and another group collected 97 sea-glass tokens. How many sea-glass tokens in all? = 126 (I) · There were 146 starfish medals in all. 31 starfish medals were used. How many starfish medals are left? = 115 (N)
- Clue 3 (Multiplication facts (1-12)): "THE TARGET WEAKENS NEAR BITTER LEMONS"3 × 9 = 27 (T) · 11 × 3 = 33 (L) · 7 × 7 = 49 (H) · 8 × 3 = 24 (W) · 12 × 4 = 48 (A) · 9 × 7 = 63 (N) · 6 × 12 = 72 (G) · 6 × 10 = 60 (R) · 10 × 8 = 80 (O) · 9 × 5 = 45 (M) · 1 × 8 = 8 (B) · 4 × 9 = 36 (S) · 10 × 4 = 40 (I) · 1 × 1 = 1 (E) · 6 × 7 = 42 (K)
- Clue 4 (Integers): "PINK HAIR TANGLES ON THE REEF CORAL"16 - (-10) = 26 (P) · (-10) + 27 = 17 (G) · 7 - (-1) = 8 (I) · (-13) + 36 = 23 (K) · (-2) + 3 = 1 (N) · (-11) + 41 = 30 (H) · (-12) + 25 = 13 (A) · 21 - (-6) = 27 (O) · (-3) + 6 = 3 (F) · (-15) + 27 = 12 (R) · (-4) + 10 = 6 (T) · (-11) + 27 = 16 (E) · 4 - (-6) = 10 (L) · (-8) + 15 = 7 (C) · (-9) + 28 = 19 (S)
- Clue 5 (Fractions of a number): surviving statement (box 6) → Sirena1/5 of 15 = 3 · 5/6 of 12 = 10 · 4/6 of 3 = 2 · 2/3 of 6 = 4 · 4/8 of 18 = 9 · 3/6 of 14 = 7 · 4/10 of 20 = 8 · 1/4 of 48 = 12 · 2/10 of 25 = 5 · 1/3 of 3 = 1 · 1/3 of 33 = 11
About this mystery
- Grade level
- Grade 7 math
- Math topics
- Fractions of a number, Bar models, Multiplication, Integers
- Reading level
- grades 7-9
- Theme
- The Case of the Missing Pearl Scepter — set in The Sunken Palace of Aquaria
- Format
- Interactive online & printable worksheet with answer key
- Solution
- One unique, verified culprit among 21 suspects