🔎 Types of sharks all of themGrade 10Reading: grades 7-9Place valueSkip countingMulti-step word problemsWord problemsMissing addends
The Mystery of the Apex Trench Saboteur
A covert intruder sabotaged the deep-sea shark observation grid at the Apex Reef Submarine Research Station! The culprit raided the telemetry deck and scrambled the tagging archives. Examine the technical clues, decode the sonar logs, and identify the culprit before they escape into the trench.
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 | Primary Rig | Gadget Tool | Tag Placement | Dorsal Fin Pattern | Deterrent Tech |
|---|---|---|---|---|---|
| Alison Kock | Whale Shark Module | Zebra Mesh | Left Fin Tagged | Striped Dorsal Fin | Copper Element |
| Valerie Taylor | Mako Shark Module | Sawfish Blade | Left Fin Tagged | Striped Dorsal Fin | Copper Element |
| Barbara Block | Great White Module | Sawfish Blade | Right Fin Tagged | Spotted Dorsal Fin | Bright Strobe |
| Ramon Bonfil | Hammerhead Module | Sawfish Blade | Right Fin Tagged | Solid Dorsal Fin | Bright Strobe |
| Gregg Skomal | Tiger Shark Module | Bull Shield | Right Fin Tagged | Striped Dorsal Fin | Bright Strobe |
| Hans Hass | Great White Module | Thresher Whip | Left Fin Tagged | Striped Dorsal Fin | Copper Element |
| Michael Domeier | Great White Module | Thresher Whip | Right Fin Tagged | Striped Dorsal Fin | Copper Element |
| Mauricio Hoyos | Great White Module | Zebra Mesh | Left Fin Tagged | Spotted Dorsal Fin | Bright Strobe |
| Riley Elliott | Whale Shark Module | Bull Shield | Left Fin Tagged | Striped Dorsal Fin | Copper Element |
| Jacques Cousteau | Great White Module | Thresher Whip | Left Fin Tagged | Spotted Dorsal Fin | Bright Strobe |
| David Attenborough | Hammerhead Module | Goblin Snout | Left Fin Tagged | Spotted Dorsal Fin | Bright Strobe |
| Andrea Marshall | Mako Shark Module | Thresher Whip | Left Fin Tagged | Spotted Dorsal Fin | Bright Strobe |
| Demeur Taylor | Mako Shark Module | Sawfish Blade | Left Fin Tagged | Striped Dorsal Fin | Bright Strobe |
| Neil Hammerschlag | Mako Shark Module | Zebra Mesh | Right Fin Tagged | Striped Dorsal Fin | Copper Element |
| Craig OConnell | Mako Shark Module | Sawfish Blade | Left Fin Tagged | Spotted Dorsal Fin | Copper Element |
| Dr Sylvia Earle | Great White Module | Goblin Snout | Left Fin Tagged | Striped Dorsal Fin | Copper Element |
| Chris Fallows | Mako Shark Module | Thresher Whip | Left Fin Tagged | Spotted Dorsal Fin | Copper Element |
| Jess Cramp | Hammerhead Module | Bull Shield | Left Fin Tagged | Solid Dorsal Fin | Bright Strobe |
| Eugenie Clark | Mako Shark Module | Zebra Mesh | Left Fin Tagged | Spotted Dorsal Fin | Bright Strobe |
| Rob Stewart | Whale Shark Module | Bull Shield | Left Fin Tagged | Spotted Dorsal Fin | Bright Strobe |
| Vicki Baracos | Mako Shark Module | Sawfish Blade | Left Fin Tagged | Striped Dorsal Fin | Acoustic Pulse |
Clue 1
Place value
To unlock the digital security log on the station dive console, analyze the place value digits in the access 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.
T
50
4000
40
400
9000
400
700
40
30
T
50
90
7000
40
400
200
7000
T
50
9000
400
40
2000
9000
6000
6000
400
4000
10
40
6000
90
What is the value of the 5 in 24,052?T
What is the value of the 9 in 48,498?D
What is the value of the 2 in 651,215?N
What is the value of the 4 in 14,266?H
What is the value of the 1 in 560,613?I
What is the value of the 2 in 32,386?B
What is the value of the 7 in 341,766?P
What is the value of the 6 in 86,079?L
What is the value of the 4 in 95,541?E
What is the value of the 3 in 240,635?C
What is the value of the 4 in 555,412?S
What is the value of the 9 in 69,318?U
What is the value of the 7 in 97,592?O
0/13 letters found
Clue 2
Skip counting
The Hydrophone Array records sonar signals in set intervals, skip count through the pulse sequences to isolate the suspect lead.
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
20
8
60
55
60
35
8
6
T
42
20
36
60
36
21
8
12
T
42
12
120
14
T
42
36
65
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, ___, 45, 48T
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, ___, 39, 42A
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, ___, 70, 80S
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, 16, 18, ___, 22, 24H
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, ___, 70, 75G
Skip-count by 2s. Fill the blank: 2, 4, 6, ___, 10, 12E
Skip-count by 2s. Fill the blank: 2, 4, ___, 8, 10C
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, ___, 24, 27L
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, ___, 16, 18N
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, ___, 130, 140I
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, ___, 14, 16F
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, ___, 60, 65U
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, ___, 40, 45P
0/13 letters found
Clue 3
Multi-step word problems
Analyzing the multi step telemetry logs requires computing total distances across several search sectors.
Solve each problem to learn its letter, then write the letters in the boxes to fill in the missing word.
Someonescaredthevillainoffwith .
C
54
69
67
67
7
28
7
81
7
80
7
N
T
There were 450 dive tanks in all. 18 dive tanks were set aside. The rest were shared equally among 8 Shark Patrol Unit. How many dive tanks did each get?C
There were 455 sonar buoys in all. 4 Shark Patrol Unit used 30 sonar buoys each. The other 5 Shark Patrol Unit shared the rest equally. How many sonar buoys did each of the other Shark Patrol Unit get?P
Marine Researcher collected 76 sonar buoys in the morning and 62 sonar buoys in the afternoon, then split them equally among 2 Shark Patrol Unit. How many sonar buoys did each get?O
There were 269 tracking probes in all. 2 Shark Patrol Unit used 13 tracking probes each. The other 3 Shark Patrol Unit shared the rest equally. How many tracking probes did each of the other Shark Patrol Unit get?L
There were 534 tracking probes in all. 2 Shark Patrol Unit used 27 tracking probes each. The other 6 Shark Patrol Unit shared the rest equally. How many tracking probes did each of the other Shark Patrol Unit get?M
Marine Researcher collected 8 dive tanks in the morning and 6 dive tanks in the afternoon, then split them equally among 2 Shark Patrol Unit. How many dive tanks did each get?E
Marine Researcher collected 32 acoustic tags in the morning and 24 acoustic tags in the afternoon, then split them equally among 2 Shark Patrol Unit. How many acoustic tags did each get?R
0/7 letters found
Clue 4
Word problems
The supply manifest lists equipment carried during the underwater excursion, solve the word problem to verify the exact counts.
Solve each problem to learn its letter, then write the letters in the boxes to fill in the missing word.
Astrandof hairturnedupatthescene.
S
99
105
11
93
98
115
9
9
O
11
S
99
A
L
F
93
N
There were 118 tracking probes. 19 were used up. How many tracking probes are left?S
There were 132 dive tanks. 34 were used up. How many dive tanks are left?P
Marine Researcher found 7 sonar buoys yesterday and 4 more today. How many sonar buoys in all?R
There were 110 tracking probes. 17 were used up. How many tracking probes are left?I
There were 30 dive tanks. 21 were used up. How many dive tanks are left?D
There were 144 acoustic tags. 39 were used up. How many acoustic tags are left?T
There were 141 tracking probes. 26 were used up. How many tracking probes are left?E
0/7 letters found
Clue 5
Missing addends — the last clue
A section of the dive log is missing data entries, find the missing addend to complete the daily dive ledger.
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
21 + ___ = 24
14 + ___ = 21
38 + ___ = 49
24 + ___ = 34
24 + ___ = 26
33 + ___ = 37
21 + ___ = 30
10 + ___ = 15
6 + ___ = 14
3 + ___ = 15
1 + ___ = 7
Step 2 — cross out the sentence with each answer
1.The villain activated the great white module, then extended a goblin snout.
2.The villain revved the mako shark module, then swept with a thresher whip.
3.The villain deployed the whale shark module, then cloaked in zebra mesh.
4.The villain fired up the hammerhead module, then extended a goblin snout.
5.The villain activated the great white module, then sliced with a sawfish blade.
6.The villain activated the great white module, then blocked with a bull shield.
7.The villain activated the great white module, then swept with a thresher whip.
8.The villain engaged the tiger shark module, then swept with a thresher whip.
9.The villain engaged the tiger shark module, then cloaked in zebra mesh.
10.The villain deployed the whale shark module, then swept with a thresher whip.
11.The villain revved the mako shark module, then sliced with a sawfish blade.
12.The villain fired up the hammerhead module, then cloaked in zebra mesh.
Solve it
Name the culprit
Choose the one suspect left standing.
Answer Key — The Mystery of the Apex Trench Saboteur
Culprit: Dr Sylvia Earle (Great White Module · Goblin Snout · Left Fin Tagged · Striped Dorsal Fin · Copper Element)
- Clue 1 (Place value): "THE SUSPECT DOES NOT USE BULL SHIELD"What is the value of the 5 in 24,052? = 50 (T) · What is the value of the 9 in 48,498? = 90 (D) · What is the value of the 2 in 651,215? = 200 (N) · What is the value of the 4 in 14,266? = 4000 (H) · What is the value of the 1 in 560,613? = 10 (I) · What is the value of the 2 in 32,386? = 2000 (B) · What is the value of the 7 in 341,766? = 700 (P) · What is the value of the 6 in 86,079? = 6000 (L) · What is the value of the 4 in 95,541? = 40 (E) · What is the value of the 3 in 240,635? = 30 (C) · What is the value of the 4 in 555,412? = 400 (S) · What is the value of the 9 in 69,318? = 9000 (U) · What is the value of the 7 in 97,592? = 7000 (O)
- Clue 2 (Skip counting): "THE SUSPECT HAS A LEFT FIN TAG"Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, ___, 45, 48 = 42 (T) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, ___, 39, 42 = 36 (A) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, ___, 70, 80 = 60 (S) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, 16, 18, ___, 22, 24 = 20 (H) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, ___, 70, 75 = 65 (G) · Skip-count by 2s. Fill the blank: 2, 4, 6, ___, 10, 12 = 8 (E) · Skip-count by 2s. Fill the blank: 2, 4, ___, 8, 10 = 6 (C) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, ___, 24, 27 = 21 (L) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, ___, 16, 18 = 14 (N) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, ___, 130, 140 = 120 (I) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, ___, 14, 16 = 12 (F) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, ___, 60, 65 = 55 (U) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, ___, 40, 45 = 35 (P)
- Clue 3 (Multi-step word problems): "COPPER ELEMENT"There were 450 dive tanks in all. 18 dive tanks were set aside. The rest were shared equally among 8 Shark Patrol Unit. How many dive tanks did each get? = 54 (C) · There were 455 sonar buoys in all. 4 Shark Patrol Unit used 30 sonar buoys each. The other 5 Shark Patrol Unit shared the rest equally. How many sonar buoys did each of the other Shark Patrol Unit get? = 67 (P) · Marine Researcher collected 76 sonar buoys in the morning and 62 sonar buoys in the afternoon, then split them equally among 2 Shark Patrol Unit. How many sonar buoys did each get? = 69 (O) · There were 269 tracking probes in all. 2 Shark Patrol Unit used 13 tracking probes each. The other 3 Shark Patrol Unit shared the rest equally. How many tracking probes did each of the other Shark Patrol Unit get? = 81 (L) · There were 534 tracking probes in all. 2 Shark Patrol Unit used 27 tracking probes each. The other 6 Shark Patrol Unit shared the rest equally. How many tracking probes did each of the other Shark Patrol Unit get? = 80 (M) · Marine Researcher collected 8 dive tanks in the morning and 6 dive tanks in the afternoon, then split them equally among 2 Shark Patrol Unit. How many dive tanks did each get? = 7 (E) · Marine Researcher collected 32 acoustic tags in the morning and 24 acoustic tags in the afternoon, then split them equally among 2 Shark Patrol Unit. How many acoustic tags did each get? = 28 (R)
- Clue 4 (Word problems): "STRIPED DORSAL FIN"There were 118 tracking probes. 19 were used up. How many tracking probes are left? = 99 (S) · There were 132 dive tanks. 34 were used up. How many dive tanks are left? = 98 (P) · Marine Researcher found 7 sonar buoys yesterday and 4 more today. How many sonar buoys in all? = 11 (R) · There were 110 tracking probes. 17 were used up. How many tracking probes are left? = 93 (I) · There were 30 dive tanks. 21 were used up. How many dive tanks are left? = 9 (D) · There were 144 acoustic tags. 39 were used up. How many acoustic tags are left? = 105 (T) · There were 141 tracking probes. 26 were used up. How many tracking probes are left? = 115 (E)
- Clue 5 (Missing addends): surviving statement (box 1) → Dr Sylvia Earle21 + ___ = 24 = 3 · 14 + ___ = 21 = 7 · 38 + ___ = 49 = 11 · 24 + ___ = 34 = 10 · 24 + ___ = 26 = 2 · 33 + ___ = 37 = 4 · 21 + ___ = 30 = 9 · 10 + ___ = 15 = 5 · 6 + ___ = 14 = 8 · 3 + ___ = 15 = 12 · 1 + ___ = 7 = 6
About this mystery
- Grade level
- Grade 10 math
- Math topics
- Place value, Skip counting, Multi-step word problems, Word problems, Missing addends
- Reading level
- grades 7-9
- Theme
- The Mystery of the Apex Trench Saboteur — set in Apex Reef Submarine Research Station
- Format
- Interactive online & printable worksheet with answer key
- Solution
- One unique, verified culprit among 21 suspects