🔎 BeachGrade 3Reading: grades 3-4Skip countingRoundingAdditionSubtractionDivision
The Mystery of Sunken Shell Cove
Someone swiped the golden trophy right before the annual Sunken Shell Cove Sandcastle Contest! The Head Lifeguard needs your help to decode the clues, track down the Beach Bandit, and save the summer festival.
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 Move | Tricky Gear | Eyewear | Hair Color | Secret Foil |
|---|---|---|---|---|---|
| Ocean Oliver | sunbeam flashing | seaweed lasso | wears sunglasses | seafoam green | cold ice cream |
| Kai Surfer | dune leaping | coconut launcher | wears sunglasses | sandy blond | squirt guns |
| Shelly Conch | wave riding | coconut launcher | wears sun visor | neon pink | squirt guns |
| Marina Wave | sunbeam flashing | crab summoner | wears sun visor | neon pink | squirt guns |
| Tide Taylor | wave riding | crab summoner | wears sunglasses | neon pink | squirt guns |
| Pearl Palms | tidal surfing | crab summoner | wears sun visor | sandy blond | bright spotlights |
| Current Chris | sandcastle blast | crab summoner | wears sun visor | sandy blond | bright spotlights |
| Coast Brody | sandcastle blast | seaweed lasso | wears sun visor | sandy blond | squirt guns |
| Wade Waters | sandcastle blast | seaweed lasso | wears sun visor | neon pink | bright spotlights |
| Reef Rivera | tidal surfing | coconut launcher | wears sun visor | sandy blond | bright spotlights |
| Finn Splash | sunbeam flashing | seaweed lasso | wears sunglasses | neon pink | bright spotlights |
| Summer Skye | sunbeam flashing | coconut launcher | wears sun visor | neon pink | bright spotlights |
| Anchor Alex | dune leaping | crab summoner | wears sun visor | neon pink | bright spotlights |
| Cove Miller | wave riding | seaweed lasso | wears sun visor | sandy blond | bright spotlights |
| Salty Sam | sandcastle blast | flip flop flinger | wears sunglasses | neon pink | bright spotlights |
| Gull Gary | sunbeam flashing | seaweed lasso | wears sunglasses | sandy blond | squirt guns |
| Captain Coral | sandcastle blast | seaweed lasso | wears sun visor | neon pink | cold ice cream |
| Sunny Ray | wave riding | seagull whistle | wears sun visor | neon pink | bright spotlights |
| Beacon Blake | wave riding | flip flop flinger | wears sunglasses | neon pink | cold ice cream |
| Baylor Beach | sunbeam flashing | seagull whistle | wears sun visor | sandy blond | squirt guns |
| Breeze Baker | dune leaping | seagull whistle | wears sun visor | neon pink | bright spotlights |
Clue 1
Skip counting
You count sets of wet footprints along the shore in equal jumps to discover where the thief fled.
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
16
35
45
110
9
39
39
20
9
10
55
25
45
60
10
25
T
16
30
60
45
20
15
12
20
21
60
30
80
80
25
10
45
12
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, ___, 18, 20T
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, ___, 50, 55E
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, ___, 42, 45L
Skip-count by 3s. Fill the blank: 3, 6, ___, 12, 15I
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, ___, 120, 130V
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, ___, 60, 65D
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, ___, 12, 14N
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, ___, 30, 35O
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, ___, 24, 27B
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, ___, 65, 70S
Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, ___, 90, 100M
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, ___, 14, 16R
Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, 16, 18, ___, 22, 24A
Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, ___, 40, 45H
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, ___, 18, 21C
Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, ___, 33, 36U
0/16 letters found
Clue 2
Rounding
The digital tide radar rounds the boat speed to the nearest ten to give a quick reading.
Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.
W
80
600
300
50
60
400
400
400
9000
W
80
9000
400
30
400
3000
60
2000
300
W
80
60
9000
5000
600
50
200
9000
400
30
50
500
600
400
40
5000
Round 84 to the nearest tenW
Round 31 to the nearest tenU
Round 475 to the nearest hundredV
Round 4,706 to the nearest thousandR
Round 9,251 to the nearest thousandA
Round 2,214 to the nearest thousandC
Round 48 to the nearest tenN
Round 645 to the nearest hundredI
Round 3,455 to the nearest thousandP
Round 59 to the nearest tenE
Round 305 to the nearest hundredT
Round 432 to the nearest hundredS
Round 40 to the nearest tenO
Round 171 to the nearest hundredG
0/14 letters found
Clue 3
Addition
You add up the lost sand buckets gathered from three different lifeguard stands.
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
371
623
605
589
788
634
851
688
850
788
850
605
688
566
851
920
589
623
T
371
850
522
270
T
371
697
920
589
623
T
371
850
T
371
270
850
T
371
270
522
T
371
623
605
540
207 + 164 =T
274 + 423 =L
362 + 272 =A
279 + 641 =I
313 + 209 =P
279 + 409 =D
252 + 314 =B
209 + 414 =H
152 + 118 =O
480 + 371 =R
294 + 295 =G
288 + 317 =E
239 + 549 =U
178 + 362 =M
368 + 482 =S
0/15 letters found
Clue 4
Subtraction
You subtract the missing beach towels from the total stack to see how many were taken.
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
612
633
452
623
123
516
896
633
393
482
148
482
516
633
482
P
612
623
482
538
179
390
623
250
390
333
333
179
516
595
123
516
482
516
833 - 221 =P
257 - 134 =C
656 - 174 =N
479 - 229 =R
603 - 270 =T
643 - 191 =L
324 - 176 =D
1147 - 251 =F
785 - 392 =U
678 - 162 =E
635 - 97 =K
496 - 317 =H
737 - 114 =I
757 - 124 =O
669 - 279 =A
860 - 265 =S
0/16 letters found
Clue 5
Division facts (1-12) — the last clue
You divide the remaining rescue whistles evenly among the patrol guards.
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
108 ÷ 12 = ?
144 ÷ 12 = ?
7 ÷ 7 = ?
48 ÷ 12 = ?
36 ÷ 6 = ?
77 ÷ 11 = ?
40 ÷ 4 = ?
56 ÷ 7 = ?
27 ÷ 9 = ?
20 ÷ 4 = ?
11 ÷ 1 = ?
Step 2 — cross out the sentence with each answer
1.The villain leaped over the high dunes, then blew a loud seagull whistle.
2.The villain flashed a bright sunbeam, then launched hard coconuts.
3.The villain flashed a bright sunbeam, then blew a loud seagull whistle.
4.The villain surfed the high tide, then flung extra flip flops.
5.The villain flashed a bright sunbeam, then flung extra flip flops.
6.The villain rode a giant wave, then swung a long seaweed lasso.
7.The villain blasted a sandcastle, then flung extra flip flops.
8.The villain leaped over the high dunes, then summoned pinch crabs.
9.The villain rode a giant wave, then blew a loud seagull whistle.
10.The villain blasted a sandcastle, then blew a loud seagull whistle.
11.The villain rode a giant wave, then launched hard coconuts.
12.The villain blasted a sandcastle, then swung a long seaweed lasso.
Solve it
Name the culprit
Choose the one suspect left standing.
Answer Key — The Mystery of Sunken Shell Cove
Culprit: Summer Skye (sunbeam flashing · coconut launcher · wears sun visor · neon pink · bright spotlights)
- Clue 1 (Skip counting): "THE VILLAIN DOES NOT USE A CRAB SUMMONER"Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, ___, 18, 20 = 16 (T) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, ___, 50, 55 = 45 (E) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, ___, 42, 45 = 39 (L) · Skip-count by 3s. Fill the blank: 3, 6, ___, 12, 15 = 9 (I) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, ___, 120, 130 = 110 (V) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, ___, 60, 65 = 55 (D) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, ___, 12, 14 = 10 (N) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, ___, 30, 35 = 25 (O) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, ___, 24, 27 = 21 (B) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, ___, 65, 70 = 60 (S) · Skip-count by 10s. Fill the blank: 10, 20, 30, 40, 50, 60, 70, ___, 90, 100 = 80 (M) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, ___, 14, 16 = 12 (R) · Skip-count by 2s. Fill the blank: 2, 4, 6, 8, 10, 12, 14, 16, 18, ___, 22, 24 = 20 (A) · Skip-count by 5s. Fill the blank: 5, 10, 15, 20, 25, 30, ___, 40, 45 = 35 (H) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, ___, 18, 21 = 15 (C) · Skip-count by 3s. Fill the blank: 3, 6, 9, 12, 15, 18, 21, 24, 27, ___, 33, 36 = 30 (U)
- Clue 2 (Rounding): "WITNESS SAW A SUSPECT WEARING A SUN VISOR"Round 84 to the nearest ten = 80 (W) · Round 31 to the nearest ten = 30 (U) · Round 475 to the nearest hundred = 500 (V) · Round 4,706 to the nearest thousand = 5000 (R) · Round 9,251 to the nearest thousand = 9000 (A) · Round 2,214 to the nearest thousand = 2000 (C) · Round 48 to the nearest ten = 50 (N) · Round 645 to the nearest hundred = 600 (I) · Round 3,455 to the nearest thousand = 3000 (P) · Round 59 to the nearest ten = 60 (E) · Round 305 to the nearest hundred = 300 (T) · Round 432 to the nearest hundred = 400 (S) · Round 40 to the nearest ten = 40 (O) · Round 171 to the nearest hundred = 200 (G)
- Clue 3 (Addition): "THE GUARDS USED BRIGHT SPOTLIGHTS TO STOP THEM"207 + 164 = 371 (T) · 274 + 423 = 697 (L) · 362 + 272 = 634 (A) · 279 + 641 = 920 (I) · 313 + 209 = 522 (P) · 279 + 409 = 688 (D) · 252 + 314 = 566 (B) · 209 + 414 = 623 (H) · 152 + 118 = 270 (O) · 480 + 371 = 851 (R) · 294 + 295 = 589 (G) · 288 + 317 = 605 (E) · 239 + 549 = 788 (U) · 178 + 362 = 540 (M) · 368 + 482 = 850 (S)
- Clue 4 (Subtraction): "POLICE FOUND NEON PINK HAIR AT THE SCENE"833 - 221 = 612 (P) · 257 - 134 = 123 (C) · 656 - 174 = 482 (N) · 479 - 229 = 250 (R) · 603 - 270 = 333 (T) · 643 - 191 = 452 (L) · 324 - 176 = 148 (D) · 1147 - 251 = 896 (F) · 785 - 392 = 393 (U) · 678 - 162 = 516 (E) · 635 - 97 = 538 (K) · 496 - 317 = 179 (H) · 737 - 114 = 623 (I) · 757 - 124 = 633 (O) · 669 - 279 = 390 (A) · 860 - 265 = 595 (S)
- Clue 5 (Division facts (1-12)): surviving statement (box 2) → Summer Skye108 ÷ 12 = 9 · 144 ÷ 12 = 12 · 7 ÷ 7 = 1 · 48 ÷ 12 = 4 · 36 ÷ 6 = 6 · 77 ÷ 11 = 7 · 40 ÷ 4 = 10 · 56 ÷ 7 = 8 · 27 ÷ 9 = 3 · 20 ÷ 4 = 5 · 11 ÷ 1 = 11
About this mystery
- Grade level
- Grade 3 math
- Math topics
- Skip counting, Rounding, Addition, Subtraction, Division
- Reading level
- grades 3-4
- Theme
- The Mystery of Sunken Shell Cove — set in Sunken Shell Cove
- Format
- Interactive online & printable worksheet with answer key
- Solution
- One unique, verified culprit among 21 suspects