Grade 3Reading: grades 3-4Place valueAdditionSubtractionRoundingMissing addends

The Cloud Island Mystery

The golden compass is gone! It was stolen right from the steering wheel of the sky ship. We must help the Sky Patrol find the thief before the clouds roll in.

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	Sky Gear	Companion Pet	Map Style	Goggle Strap	Fear
Marlo Mapmaker	grappling hook	flying squirrel	right handed writer	gold ribbon	bright lights
Zephyr Zoom	cloud boots	mini blimp	right handed writer	gold ribbon	bright lights
Wendy Wing	brass jetpack	mechanical owl	right handed writer	striped rope	tickly feathers
Breezy Bob	grappling hook	flying squirrel	right handed writer	striped rope	bright lights
Max Altitude	brass jetpack	cloud ferret	right handed writer	gold ribbon	squeaky toys
Leo Lookout	cloud boots	cloud ferret	right handed writer	blue leather	bright lights
Daisy Dare	brass jetpack	mini blimp	right handed writer	blue leather	bright lights
Captain Barnaby	brass jetpack	flying squirrel	right handed writer	gold ribbon	tickly feathers
Gale Windward	brass jetpack	mechanical owl	left handed writer	gold ribbon	tickly feathers
Toby Turbo	brass jetpack	mini blimp	left handed writer	striped rope	tickly feathers
Dash Horizon	wind glider	mini blimp	right handed writer	gold ribbon	squeaky toys
Skip Skipper	brass jetpack	parakeet	right handed writer	striped rope	tickly feathers
Skyler Storm	grappling hook	flying squirrel	right handed writer	striped rope	squeaky toys
Oliver Owl	brass jetpack	flying squirrel	left handed writer	gold ribbon	bright lights
Rusty Rivets	turbo propeller	mini blimp	left handed writer	blue leather	bright lights
Finn Feather	turbo propeller	cloud ferret	left handed writer	gold ribbon	bright lights
Bella Balloon	turbo propeller	mechanical owl	right handed writer	gold ribbon	bright lights
Cody Compass	brass jetpack	flying squirrel	right handed writer	gold ribbon	bright lights
Piper Propeller	brass jetpack	mechanical owl	right handed writer	striped rope	bright lights
Sammy Sky	brass jetpack	parakeet	left handed writer	gold ribbon	tickly feathers
Gemma Gear	grappling hook	mini blimp	right handed writer	gold ribbon	bright lights

Clue 1

Place value

The ship computer asks for the value of the digit in the tens place to unlock the first clue file.

Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.

100

8000

100

400

8000

5000

9000

3000

8000

7000

200

3000

100

4000

8000

4000

8000

4000

200

400

4000

900

3000

900

What is the value of the 1 in 129?T

What is the value of the 5 in 9,856?M

What is the value of the 6 in 4,465?W

What is the value of the 8 in 281?V

What is the value of the 4 in 421?I

What is the value of the 9 in 793?C

What is the value of the 3 in 63,865?O

What is the value of the 2 in 8,218?N

What is the value of the 7 in 7,944?S

What is the value of the 9 in 9,408?D

What is the value of the 8 in 98,513?E

What is the value of the 2 in 124?H

What is the value of the 4 in 4,507?A

What is the value of the 5 in 5,101?F

What is the value of the 9 in 6,974?L

0/15 letters found

Clue 2

Addition

To track the thief we must add all the heavy gear crates loaded onto the deck this morning.

Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.

682

628

237

233

628

728

684

747

628

476

684

535

240

237

747

829

747

596

519

643

476

535

240

829

240

519

237

445 + 237 =L

425 + 218 =D

107 + 126 =B

178 + 298 =W

233 + 514 =H

463 + 265 =K

133 + 104 =G

363 + 233 =A

332 + 187 =N

125 + 115 =I

263 + 365 =O

567 + 262 =T

202 + 333 =R

326 + 358 =S

0/14 letters found

Clue 3

Subtraction

We find a scrap of paper under the seat after we subtract the torn pages from the logbook.

Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.

893

174

239

386

533

293

239

554

533

121

864

658

322

121

492

154

174

893

533

293

544

754

174

293

492

154

174

893

754

1160 - 267 =T

166 - 45 =R

945 - 287 =M

936 - 382 =D

561 - 322 =E

475 - 182 =L

854 - 321 =F

301 - 147 =G

773 - 387 =Y

655 - 163 =I

468 - 294 =H

581 - 37 =A

922 - 58 =O

437 - 115 =B

831 - 77 =S

0/15 letters found

Clue 4

Rounding

The radar screen only shows rounded miles so we must estimate the distance to get the next clue.

Solve each problem to learn its letter. Then write that letter in every box that shows the same number, and read the secret clue.

2000

900

500

3000

600

9000

8000

3000

4000

400

500

7000

8000

5000

500

3000

600

300

900

500

700

Round 2,060 to the nearest thousandW

Round 8,203 to the nearest thousandI

Round 81 to the nearest tenH

Round 6,636 to the nearest thousandR

Round 48 to the nearest tenL

Round 481 to the nearest hundredO

Round 36 to the nearest tenC

Round 17 to the nearest tenF

Round 294 to the nearest hundredT

Round 5,456 to the nearest thousandB

Round 358 to the nearest hundredG

Round 64 to the nearest tenD

Round 2,527 to the nearest thousandN

Round 678 to the nearest hundredK

Round 887 to the nearest hundredE

Round 3,938 to the nearest thousandY

Round 642 to the nearest hundredA

Round 30 to the nearest tenU

Round 8,863 to the nearest thousandS

0/19 letters found

Clue 5

Missing addends — the last clue

We need to find how many fuel cans are missing from the rack to crack the final safe lock.

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

3 + ___ = 10

3 + ___ = 7

8 + ___ = 13

2 + ___ = 14

2 + ___ = 11

7 + ___ = 15

4 + ___ = 6

8 + ___ = 19

7 + ___ = 17

9 + ___ = 15

3 + ___ = 6

Step 2 — cross out the sentence with each answer

1.The villain swings from a grappling hook, then launches a mini blimp to block the view.

2.The villain flies up using a turbo propeller, then hides a cloud ferret in the captain cabin.

3.The villain bounces high in cloud boots, then lets a flying squirrel glide away with the map.

4.The villain bounces high in cloud boots, then launches a mini blimp to block the view.

5.The villain zooms past on a brass jetpack, then lets a flying squirrel glide away with the map.

6.The villain zooms past on a brass jetpack, then hides a cloud ferret in the captain cabin.

7.The villain swings from a grappling hook, then lets a flying squirrel glide away with the map.

8.The villain swings from a grappling hook, then hides a cloud ferret in the captain cabin.

9.The villain sails through the air on a wind glider, then commands their pet parakeet to snatch the compass.

10.The villain flies up using a turbo propeller, then launches a mini blimp to block the view.

11.The villain flies up using a turbo propeller, then lets a flying squirrel glide away with the map.

12.The villain sails through the air on a wind glider, then hides a cloud ferret in the captain cabin.

Solve it

Name the culprit

Choose the one suspect left standing.

Answer Key — The Cloud Island Mystery

Culprit: Gemma Gear (grappling hook · mini blimp · right handed writer · gold ribbon · bright lights)

Clue 1 (Place value): "THE THIEF DOES NOT HAVE A MECHANICAL OWL"
What is the value of the 1 in 129? = 100 (T) · What is the value of the 5 in 9,856? = 50 (M) · What is the value of the 6 in 4,465? = 60 (W) · What is the value of the 8 in 281? = 80 (V) · What is the value of the 4 in 421? = 400 (I) · What is the value of the 9 in 793? = 90 (C) · What is the value of the 3 in 63,865? = 3000 (O) · What is the value of the 2 in 8,218? = 200 (N) · What is the value of the 7 in 7,944? = 7000 (S) · What is the value of the 9 in 9,408? = 9000 (D) · What is the value of the 8 in 98,513? = 8000 (E) · What is the value of the 2 in 124? = 20 (H) · What is the value of the 4 in 4,507? = 4000 (A) · What is the value of the 5 in 5,101? = 5000 (F) · What is the value of the 9 in 6,974? = 900 (L)
Clue 2 (Addition): "LOG BOOK SHOWS RIGHT HAND WRITING"
445 + 237 = 682 (L) · 425 + 218 = 643 (D) · 107 + 126 = 233 (B) · 178 + 298 = 476 (W) · 233 + 514 = 747 (H) · 463 + 265 = 728 (K) · 133 + 104 = 237 (G) · 363 + 233 = 596 (A) · 332 + 187 = 519 (N) · 125 + 115 = 240 (I) · 263 + 365 = 628 (O) · 567 + 262 = 829 (T) · 202 + 333 = 535 (R) · 326 + 358 = 684 (S)
Clue 3 (Subtraction): "THEY FLED FROM BRIGHT FLASHLIGHTS"
1160 - 267 = 893 (T) · 166 - 45 = 121 (R) · 945 - 287 = 658 (M) · 936 - 382 = 554 (D) · 561 - 322 = 239 (E) · 475 - 182 = 293 (L) · 854 - 321 = 533 (F) · 301 - 147 = 154 (G) · 773 - 387 = 386 (Y) · 655 - 163 = 492 (I) · 468 - 294 = 174 (H) · 581 - 37 = 544 (A) · 922 - 58 = 864 (O) · 437 - 115 = 322 (B) · 831 - 77 = 754 (S)
Clue 4 (Rounding): "WE FOUND A SHINY GOLD RIBBON AT THE DOCK"
Round 2,060 to the nearest thousand = 2000 (W) · Round 8,203 to the nearest thousand = 8000 (I) · Round 81 to the nearest ten = 80 (H) · Round 6,636 to the nearest thousand = 7000 (R) · Round 48 to the nearest ten = 50 (L) · Round 481 to the nearest hundred = 500 (O) · Round 36 to the nearest ten = 40 (C) · Round 17 to the nearest ten = 20 (F) · Round 294 to the nearest hundred = 300 (T) · Round 5,456 to the nearest thousand = 5000 (B) · Round 358 to the nearest hundred = 400 (G) · Round 64 to the nearest ten = 60 (D) · Round 2,527 to the nearest thousand = 3000 (N) · Round 678 to the nearest hundred = 700 (K) · Round 887 to the nearest hundred = 900 (E) · Round 3,938 to the nearest thousand = 4000 (Y) · Round 642 to the nearest hundred = 600 (A) · Round 30 to the nearest ten = 30 (U) · Round 8,863 to the nearest thousand = 9000 (S)
Clue 5 (Missing addends): surviving statement (box 1) → Gemma Gear
3 + ___ = 10 = 7 · 3 + ___ = 7 = 4 · 8 + ___ = 13 = 5 · 2 + ___ = 14 = 12 · 2 + ___ = 11 = 9 · 7 + ___ = 15 = 8 · 4 + ___ = 6 = 2 · 8 + ___ = 19 = 11 · 7 + ___ = 17 = 10 · 9 + ___ = 15 = 6 · 3 + ___ = 6 = 3

About this mystery

Grade level: Grade 3 math
Math topics: Place value, Addition, Subtraction, Rounding, Missing addends
Reading level: grades 3-4
Theme: The Cloud Island Mystery — set in the floating docks of Cloud Island
Format: Interactive online & printable worksheet with answer key
Solution: One unique, verified culprit among 21 suspects

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