Math MysteriesMake a mystery

CRACK THE CODE · GRADE 2

The Obsidian Chest Cipher

Find the missing numbers hidden behind the Minecraft block shapes to solve the math equations and reveal the four-digit code for the obsidian vault.

Each shape stands for a number. Then solve the shape equations and read off the 4-digit code. Do it here or print the sheet — the answer key comes with it.

The key

=7
=1
=2
=5
=6

Every symbol is a whole number from 1 to 10. A number in front of a shape means multiply: 2 stars = 2 x star.

Crack these

  1. 1.2−=
  2. 2.2+2=CODE 1
  3. 3.+2=
  4. 4.2+2=CODE 2
  5. 5.2+=
  6. 6.−=CODE 3
  7. 7.+2=
  8. 8.3−=CODE 4
  9. 9.?+=9Which shape?
  10. 10.?+=13Which shape?

The vault code

Take the ones digit of your answers to problems 2, 4, 6, 8 (the ones tagged CODE 1–4), in that order. That opens the obsidian vault containing.

Show answer key (for grown-ups)

Key: triangle = 7 · hexagon = 1 · diamond = 2 · cross = 5 · pentagon = 6

Every symbol is a whole number from 1 to 10.

1.2 x hexagon - diamond0
2.2 x diamond + 2 x hexagon6
3.hexagon + 2 x pentagon13
4.2 x cross + 2 x pentagon22
5.2 x diamond + hexagon5
6.pentagon - cross1
7.diamond + 2 x cross12
8.3 x triangle - diamond19
9.? + triangle = 9diamond
10.? + pentagon = 13triangle

Vault code: 6219

About Crack the Code

Crack the Code is early algebra without the letters: a key maps shapes to numbers, and the kid substitutes, computes, and — from grade 3 up — deduces hidden values from shape equations before they can solve anything. Grade 2 practices addition, subtraction, and multiplying by 2 and 3. Every sheet has exactly one right key and one right code.

It's one of three things Math Mysteries makes, free and printable, personalized to what your kid is into: a full math mystery whodunit, a Lab Work sheet of multi-step word problems, or a Crack the Code sheet like this one. Browse free printable worksheets by grade, skill, and theme.

Keep exploring

Free Printable Math Mystery Worksheets (Grades 1–5)
Hundreds of free, printable math mystery worksheets — pick a grade, print the case, and your kid solves math to catch the culprit.
Math Mystery Games for a Kid Who Hates Worksheets
An honest guide to detective-style math for kids who groan at drills — what actually works, and when a mystery beats a game.
Detective Math: Story-Driven Practice for Ages 6–12
How whodunit math turns arithmetic into deduction — the method, the research-backed why, and how to start today for free.