Grade 4Reading: grades 3-4Place valueSkip countingWord problemsMulti-step word problemsDivision
The Mystery of Sunken Key
Someone snuck into the Harbor Master office and snatched the ancient treasure map! Use your detective skills and solve the math clues to discover who took it.
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 | Gadget | Badge | Dominant Hand | Bandana Color | Fear |
|---|---|---|---|---|---|
| Barnaby Beach | Decoder Ring | Silver Anchor | Left handed | Green Bandana | Afraid of Spiders |
| Zane Zephyr | Brass Compass | Bronze Compass | Left handed | Red Bandana | Afraid of Storms |
| Grace Gull | Smoke Bomb | Golden Feather | Left handed | Red Bandana | Afraid of Parrots |
| Vince Voyage | Decoder Ring | Bronze Compass | Right handed | Blue Bandana | Afraid of Storms |
| Leo Lagoon | Brass Compass | Ruby Skull | Right handed | Blue Bandana | Afraid of Storms |
| Hank Haven | Pocket Telescope | Bronze Compass | Right handed | Green Bandana | Afraid of Parrots |
| Opal Ocean | Smoke Bomb | Golden Feather | Right handed | Red Bandana | Afraid of Parrots |
| Rory Ripple | Grappling Hook | Ruby Skull | Left handed | Green Bandana | Afraid of Spiders |
| Nico Nautilus | Grappling Hook | Golden Feather | Left handed | Red Bandana | Afraid of Storms |
| Mina Marina | Smoke Bomb | Ruby Skull | Right handed | Red Bandana | Afraid of Storms |
| Kira Kelp | Brass Compass | Golden Feather | Left handed | Green Bandana | Afraid of Spiders |
| Quinn Reef | Grappling Hook | Ruby Skull | Left handed | Blue Bandana | Afraid of Spiders |
| Pete Pelican | Pocket Telescope | Bronze Compass | Left handed | Green Bandana | Afraid of Storms |
| Carly Coral | Smoke Bomb | Bronze Compass | Left handed | Green Bandana | Afraid of Spiders |
| Ella Ebbtide | Pocket Telescope | Golden Feather | Right handed | Red Bandana | Afraid of Parrots |
| Toby Trawler | Pocket Telescope | Golden Feather | Left handed | Green Bandana | Afraid of Spiders |
| Xander Yole | Pocket Telescope | Ruby Skull | Right handed | Red Bandana | Afraid of Spiders |
| Finn Guppy | Grappling Hook | Emerald Palm | Right handed | Green Bandana | Afraid of Spiders |
| Ula Urchin | Decoder Ring | Silver Anchor | Left handed | Green Bandana | Afraid of Storms |
| Willa Wave | Grappling Hook | Golden Feather | Left handed | Green Bandana | Afraid of Parrots |
| Drake Drift | Decoder Ring | Ruby Skull | Right handed | Red Bandana | Afraid of Storms |
Clue 1
Place value
You find a mysterious digit lock on the sea chest that reveals a place value puzzle.
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
800
3000
10
60
80
50
50
900
80
300
100
7000
10
70
300
7000
T
800
3000
900
60
10
900
90
30
7000
300
9000
10
200
7000
2000
40
900
70
70
What is the value of the 8 in 805?T
What is the value of the 9 in 933?A
What is the value of the 6 in 5,364?V
What is the value of the 8 in 6,789?I
What is the value of the 2 in 32,007?M
What is the value of the 7 in 7,864?O
What is the value of the 9 in 1,695?B
What is the value of the 3 in 308?N
What is the value of the 3 in 838?R
What is the value of the 3 in 93,581?H
What is the value of the 4 in 142?P
What is the value of the 2 in 297?C
What is the value of the 1 in 6,149?D
What is the value of the 9 in 9,654?Z
What is the value of the 5 in 1,651?L
What is the value of the 7 in 678?S
What is the value of the 1 in 6,218?E
0/17 letters found
Clue 2
Skip counting
Footprints on the beach jump in equal steps along the sand dunes.
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
21
45
100
6
36
T
21
39
100
14
14
14
90
6
90
18
100
8
T
21
45
90
39
42
100
42
22
36
18
18
90
36
39
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, ___, 24, 27T
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, ___, 24, 26V
Skip-count by 2s. Fill the blank: 2, 4, 6, ___, 10, 12F
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, ___, 50, 55H
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, ___, 45, 48D
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, ___, 21, 24L
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, ___, 100, 110A
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, ___, 110, 120E
Skip-count by 2s. Fill the blank: 2, 4, ___, 8, 10W
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, ___, 39, 42I
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, ___, 16, 18S
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, ___, 42, 45N
0/12 letters found
Clue 3
Word problems
A note in a bottle challenges you to solve a story about island supplies.
Solve each problem to learn its letter, then write the letters in the boxes to fill in the missing word.
Someonescaredthevillainoffwith .
A
41
80
25
A
41
46
59
64
80
42
P
46
59
E
25
42
Captain found 4 spyglasses yesterday and 37 more today. How many spyglasses in all?A
There were 92 compasses. 12 were used up. How many compasses are left?F
There were 63 lanterns. 4 were used up. How many lanterns are left?D
Captain found 39 rope coils yesterday and 3 more today. How many rope coils in all?S
Captain found 10 spyglasses yesterday and 36 more today. How many spyglasses in all?I
Captain lined up 8 rows of 8 compasses. How many compasses in all?O
There were 51 lanterns. 26 were used up. How many lanterns are left?R
0/7 letters found
Clue 4
Multi-step word problems
A map on the table requires solving two connected clues about trail steps.
Solve each problem to learn its letter, then write the letters in the boxes to fill in the missing word.
Astrandofhairturnedupatthescene.
G
22
36
16
16
75
55
11
75
30
11
75
11
There were 143 lanterns in all. 3 Deckhands used 11 lanterns each. The other 5 Deckhands shared the rest equally. How many lanterns did each of the other Deckhands get?G
Captain collected 87 gold doubloons in the morning and 9 gold doubloons in the afternoon, then split them equally among 6 Deckhands. How many gold doubloons did each get?E
There were 203 compasses in all. 23 compasses were set aside. The rest were shared equally among 5 Deckhands. How many compasses did each get?R
Captain earned 3 spyglasses in each of 2 rounds, plus 72 bonus spyglasses. Then 3 spyglasses were lost. How many spyglasses are left?N
Captain filled 7 boxes with 2 gold doubloons each, then found 41 more gold doubloons. How many gold doubloons are there in all?B
Captain earned 4 compasses in each of 5 rounds, plus 13 bonus compasses. Then 3 compasses were lost. How many compasses are left?D
Captain filled 5 boxes with 2 rope coils each, then found 1 more rope coils. How many rope coils are there in all?A
0/7 letters found
Clue 5
Division facts (1-12) — the last clue
To unlock the final cave door you must divide the shiny coins equally.
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 ÷ 7 = ?
90 ÷ 9 = ?
72 ÷ 8 = ?
5 ÷ 5 = ?
99 ÷ 9 = ?
32 ÷ 8 = ?
15 ÷ 3 = ?
48 ÷ 8 = ?
14 ÷ 7 = ?
14 ÷ 2 = ?
84 ÷ 7 = ?
Step 2 — cross out the sentence with each answer
1.The villain cracked a secret decoder, then wore an emerald palm.
2.The villain checked the brass compass, then held up a ruby skull.
3.The villain spied through a telescope, then showed off a golden feather.
4.The villain spied through a telescope, then wore an emerald palm.
5.The villain checked the brass compass, then pinned on a silver anchor.
6.The villain dropped a smoke bomb, then held up a ruby skull.
7.The villain cracked a secret decoder, then flashed a bronze compass.
8.The villain checked the brass compass, then showed off a golden feather.
9.The villain cracked a secret decoder, then pinned on a silver anchor.
10.The villain swung across on a rope, then held up a ruby skull.
11.The villain checked the brass compass, then flashed a bronze compass.
12.The villain dropped a smoke bomb, then pinned on a silver anchor.
Solve it
Name the culprit
Choose the one suspect left standing.
Answer Key — The Mystery of Sunken Key
Culprit: Kira Kelp (Brass Compass · Golden Feather · Left handed · Green Bandana · Afraid of Spiders)
- Clue 1 (Place value): "THE VILLAIN DOES NOT HAVE A BRONZE COMPASS"What is the value of the 8 in 805? = 800 (T) · What is the value of the 9 in 933? = 900 (A) · What is the value of the 6 in 5,364? = 60 (V) · What is the value of the 8 in 6,789? = 80 (I) · What is the value of the 2 in 32,007? = 2000 (M) · What is the value of the 7 in 7,864? = 7000 (O) · What is the value of the 9 in 1,695? = 90 (B) · What is the value of the 3 in 308? = 300 (N) · What is the value of the 3 in 838? = 30 (R) · What is the value of the 3 in 93,581? = 3000 (H) · What is the value of the 4 in 142? = 40 (P) · What is the value of the 2 in 297? = 200 (C) · What is the value of the 1 in 6,149? = 100 (D) · What is the value of the 9 in 9,654? = 9000 (Z) · What is the value of the 5 in 1,651? = 50 (L) · What is the value of the 7 in 678? = 70 (S) · What is the value of the 1 in 6,218? = 10 (E)
- Clue 2 (Skip counting): "THE WITNESS SAW A LEFT HANDED VILLAIN"Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, ___, 24, 27 = 21 (T) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, ___, 24, 26 = 22 (V) · Skip-count by 2s. Fill the blank: 2, 4, 6, ___, 10, 12 = 8 (F) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, ___, 50, 55 = 45 (H) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, ___, 45, 48 = 42 (D) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, ___, 21, 24 = 18 (L) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, ___, 100, 110 = 90 (A) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, ___, 110, 120 = 100 (E) · Skip-count by 2s. Fill the blank: 2, 4, ___, 8, 10 = 6 (W) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, ___, 39, 42 = 36 (I) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, ___, 16, 18 = 14 (S) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, ___, 42, 45 = 39 (N)
- Clue 3 (Word problems): "AFRAID OF SPIDERS"Captain found 4 spyglasses yesterday and 37 more today. How many spyglasses in all? = 41 (A) · There were 92 compasses. 12 were used up. How many compasses are left? = 80 (F) · There were 63 lanterns. 4 were used up. How many lanterns are left? = 59 (D) · Captain found 39 rope coils yesterday and 3 more today. How many rope coils in all? = 42 (S) · Captain found 10 spyglasses yesterday and 36 more today. How many spyglasses in all? = 46 (I) · Captain lined up 8 rows of 8 compasses. How many compasses in all? = 64 (O) · There were 51 lanterns. 26 were used up. How many lanterns are left? = 25 (R)
- Clue 4 (Multi-step word problems): "GREEN BANDANA"There were 143 lanterns in all. 3 Deckhands used 11 lanterns each. The other 5 Deckhands shared the rest equally. How many lanterns did each of the other Deckhands get? = 22 (G) · Captain collected 87 gold doubloons in the morning and 9 gold doubloons in the afternoon, then split them equally among 6 Deckhands. How many gold doubloons did each get? = 16 (E) · There were 203 compasses in all. 23 compasses were set aside. The rest were shared equally among 5 Deckhands. How many compasses did each get? = 36 (R) · Captain earned 3 spyglasses in each of 2 rounds, plus 72 bonus spyglasses. Then 3 spyglasses were lost. How many spyglasses are left? = 75 (N) · Captain filled 7 boxes with 2 gold doubloons each, then found 41 more gold doubloons. How many gold doubloons are there in all? = 55 (B) · Captain earned 4 compasses in each of 5 rounds, plus 13 bonus compasses. Then 3 compasses were lost. How many compasses are left? = 30 (D) · Captain filled 5 boxes with 2 rope coils each, then found 1 more rope coils. How many rope coils are there in all? = 11 (A)
- Clue 5 (Division facts (1-12)): surviving statement (box 8) → Kira Kelp21 ÷ 7 = 3 · 90 ÷ 9 = 10 · 72 ÷ 8 = 9 · 5 ÷ 5 = 1 · 99 ÷ 9 = 11 · 32 ÷ 8 = 4 · 15 ÷ 3 = 5 · 48 ÷ 8 = 6 · 14 ÷ 7 = 2 · 14 ÷ 2 = 7 · 84 ÷ 7 = 12
About this mystery
- Grade level
- Grade 4 math
- Math topics
- Place value, Skip counting, Word problems, Multi-step word problems, Division
- Reading level
- grades 3-4
- Theme
- The Mystery of Sunken Key — set in Sunken Key Cove
- Format
- Interactive online & printable worksheet with answer key
- Solution
- One unique, verified culprit among 21 suspects