Grade 3Reading: grades 1-2RoundingAdditionSubtractionMultiplicationDivision
The Treehouse Island Mystery
Someone took the legendary Golden Juice Box from the treehouse vault! As the junior detective, you need to follow the footprints and solve the math clues to find out who did 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 | Explorer Tool | Backpack Gear | Writing Hand | Hair Color | Distraction |
|---|---|---|---|---|---|
| Ella | slide whistle | shiny badge | right handed | brown hair | bubble gum |
| Maya | slide whistle | juice pack | left handed | brown hair | bubble gum |
| Grace | binocular map | laser pointer | left handed | brown hair | funny joke |
| Sam | binocular map | juice pack | left handed | yellow hair | bubble gum |
| Luke | secret compass | shiny badge | right handed | yellow hair | squeaky toy |
| Owen | slide whistle | shiny badge | left handed | brown hair | bubble gum |
| Lily | glow lantern | mud boots | left handed | yellow hair | bubble gum |
| Sophie | slide whistle | mud boots | right handed | yellow hair | bubble gum |
| Jack | secret compass | juice pack | left handed | red hair | bubble gum |
| Cole | binocular map | laser pointer | left handed | brown hair | squeaky toy |
| Mia | binocular map | laser pointer | right handed | yellow hair | squeaky toy |
| Jake | glow lantern | mud boots | right handed | red hair | funny joke |
| Emma | binocular map | mud boots | left handed | brown hair | squeaky toy |
| Liam | glow lantern | mud boots | left handed | red hair | funny joke |
| Abby | binocular map | juice pack | left handed | brown hair | bubble gum |
| Chloe | glow lantern | juice pack | right handed | red hair | funny joke |
| Zoe | glow lantern | laser pointer | right handed | brown hair | bubble gum |
| Nora | grappling hook | chalk box | right handed | brown hair | squeaky toy |
| Leo | binocular map | chalk box | left handed | brown hair | bubble gum |
| Finn | secret compass | mud boots | left handed | brown hair | bubble gum |
| Toby | binocular map | laser pointer | left handed | red hair | bubble gum |
Clue 1
Rounding
Our treehouse map shows a fuzzy number. We must round it to the nearest ten to find the coordinates.
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
80
60
20
600
200
8000
8000
9000
200
700
2000
3000
20
90
700
3000
T
80
60
9000
600
20
9000
800
60
9000
8000
50
400
3000
900
Round 79 to the nearest tenT
Round 3,485 to the nearest thousandO
Round 87 to the nearest tenS
Round 50 to the nearest tenK
Round 18 to the nearest tenE
Round 8,553 to the nearest thousandA
Round 435 to the nearest hundredB
Round 1,675 to the nearest thousandD
Round 199 to the nearest hundredI
Round 631 to the nearest hundredV
Round 693 to the nearest hundredN
Round 63 to the nearest tenH
Round 7,620 to the nearest thousandL
Round 758 to the nearest hundredC
Round 901 to the nearest hundredX
0/15 letters found
Clue 2
Addition
We need to count all our walkie-talkies. We add the old ones and the new ones together.
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
507
310
396
528
566
987
566
T
507
495
498
534
987
396
816
T
507
310
396
566
498
820
396
825
T
507
310
558
918
816
T
507
495
351
498
566
T
507
396
219 + 288 =T
229 + 329 =A
503 + 415 =N
433 + 387 =L
192 + 374 =I
331 + 167 =R
307 + 188 =O
527 + 298 =F
330 + 198 =V
209 + 142 =W
255 + 279 =U
224 + 172 =E
308 + 508 =D
528 + 459 =S
120 + 190 =H
0/15 letters found
Clue 3
Subtraction
A sneaky squirrel took some of our spy badges. Let us subtract them to see what is left.
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
449
458
890
434
808
890
703
377
238
245
833
890
635
703
434
T
449
867
703
323
323
890
619
551
238
551
872
551
551
156
890
625
872
624
727 - 278 =T
684 - 226 =H
839 - 220 =D
673 - 122 =B
946 - 311 =W
943 - 76 =R
1220 - 387 =O
828 - 125 =A
970 - 80 =E
995 - 123 =U
762 - 137 =G
620 - 375 =F
805 - 371 =S
1035 - 227 =N
672 - 295 =K
514 - 358 =L
367 - 129 =Y
368 - 45 =P
731 - 107 =M
0/19 letters found
Clue 4
Multiplication facts (1-12)
We pack our snack boxes in neat rows. We multiply the rows to find how many we have.
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
48
40
2
4
96
100
64
60
24
25
66
60
100
64
4
2
64
60
66
88
1
66
4
W
48
100
99
60
33
66
12 × 4 =W
11 × 3 =I
2 × 12 =S
5 × 5 =T
1 × 4 =O
8 × 8 =D
2 × 1 =F
10 × 6 =A
11 × 8 =K
8 × 12 =U
1 × 1 =B
10 × 10 =N
11 × 9 =H
4 × 10 =E
6 × 11 =R
0/15 letters found
Clue 5
Division facts (1-12) — the last clue
We want to share our map pieces equally. We divide them among our team members.
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
30 ÷ 3 = ?
108 ÷ 12 = ?
10 ÷ 5 = ?
16 ÷ 2 = ?
77 ÷ 11 = ?
48 ÷ 12 = ?
24 ÷ 4 = ?
18 ÷ 6 = ?
40 ÷ 8 = ?
33 ÷ 3 = ?
3 ÷ 3 = ?
Step 2 — cross out the sentence with each answer
1.The villain swings on a rope, then pins on a metal star.
2.The villain plays a loud tune, then pins on a metal star.
3.The villain looks through the lens, then shines a red dot.
4.The villain looks through the lens, then splashes in a puddle.
5.The villain checks the needle, then sips a sweet drink.
6.The villain swings on a rope, then splashes in a puddle.
7.The villain swings on a rope, then shines a red dot.
8.The villain lights up the dark, then shines a red dot.
9.The villain looks through the lens, then sips a sweet drink.
10.The villain plays a loud tune, then sips a sweet drink.
11.The villain plays a loud tune, then shines a red dot.
12.The villain checks the needle, then splashes in a puddle.
Solve it
Name the culprit
Choose the one suspect left standing.
Answer Key — The Treehouse Island Mystery
Culprit: Finn (secret compass · mud boots · left handed · brown hair · bubble gum)
- Clue 1 (Rounding): "THE VILLAIN DOES NOT HAVE A CHALK BOX"Round 79 to the nearest ten = 80 (T) · Round 3,485 to the nearest thousand = 3000 (O) · Round 87 to the nearest ten = 90 (S) · Round 50 to the nearest ten = 50 (K) · Round 18 to the nearest ten = 20 (E) · Round 8,553 to the nearest thousand = 9000 (A) · Round 435 to the nearest hundred = 400 (B) · Round 1,675 to the nearest thousand = 2000 (D) · Round 199 to the nearest hundred = 200 (I) · Round 631 to the nearest hundred = 600 (V) · Round 693 to the nearest hundred = 700 (N) · Round 63 to the nearest ten = 60 (H) · Round 7,620 to the nearest thousand = 8000 (L) · Round 758 to the nearest hundred = 800 (C) · Round 901 to the nearest hundred = 900 (X)
- Clue 2 (Addition): "THE VISITOR USED THEIR LEFT HAND TO WRITE"219 + 288 = 507 (T) · 229 + 329 = 558 (A) · 503 + 415 = 918 (N) · 433 + 387 = 820 (L) · 192 + 374 = 566 (I) · 331 + 167 = 498 (R) · 307 + 188 = 495 (O) · 527 + 298 = 825 (F) · 330 + 198 = 528 (V) · 209 + 142 = 351 (W) · 255 + 279 = 534 (U) · 224 + 172 = 396 (E) · 308 + 508 = 816 (D) · 528 + 459 = 987 (S) · 120 + 190 = 310 (H)
- Clue 3 (Subtraction): "THE SNEAKY FOE WAS TRAPPED BY BUBBLE GUM"727 - 278 = 449 (T) · 684 - 226 = 458 (H) · 839 - 220 = 619 (D) · 673 - 122 = 551 (B) · 946 - 311 = 635 (W) · 943 - 76 = 867 (R) · 1220 - 387 = 833 (O) · 828 - 125 = 703 (A) · 970 - 80 = 890 (E) · 995 - 123 = 872 (U) · 762 - 137 = 625 (G) · 620 - 375 = 245 (F) · 805 - 371 = 434 (S) · 1035 - 227 = 808 (N) · 672 - 295 = 377 (K) · 514 - 358 = 156 (L) · 367 - 129 = 238 (Y) · 368 - 45 = 323 (P) · 731 - 107 = 624 (M)
- Clue 4 (Multiplication facts (1-12)): "WE FOUND A STRAND OF DARK BROWN HAIR"12 × 4 = 48 (W) · 11 × 3 = 33 (I) · 2 × 12 = 24 (S) · 5 × 5 = 25 (T) · 1 × 4 = 4 (O) · 8 × 8 = 64 (D) · 2 × 1 = 2 (F) · 10 × 6 = 60 (A) · 11 × 8 = 88 (K) · 8 × 12 = 96 (U) · 1 × 1 = 1 (B) · 10 × 10 = 100 (N) · 11 × 9 = 99 (H) · 4 × 10 = 40 (E) · 6 × 11 = 66 (R)
- Clue 5 (Division facts (1-12)): surviving statement (box 12) → Finn30 ÷ 3 = 10 · 108 ÷ 12 = 9 · 10 ÷ 5 = 2 · 16 ÷ 2 = 8 · 77 ÷ 11 = 7 · 48 ÷ 12 = 4 · 24 ÷ 4 = 6 · 18 ÷ 6 = 3 · 40 ÷ 8 = 5 · 33 ÷ 3 = 11 · 3 ÷ 3 = 1
About this mystery
- Grade level
- Grade 3 math
- Math topics
- Rounding, Addition, Subtraction, Multiplication, Division
- Reading level
- grades 1-2
- Theme
- The Treehouse Island Mystery — set in a backyard treehouse with rope bridges and hidden maps
- Format
- Interactive online & printable worksheet with answer key
- Solution
- One unique, verified culprit among 21 suspects