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CRACK THE CODE · GRADE 1

Crack the Vault Code

Someone locked the vault with a 4-digit code. Work out what each shape is worth and crack it.

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.

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The key

=1
=8
=7
=4

Every symbol is a whole number from 1 to 9.

Crack these

  1. 1.+2=
  2. 2.11−=CODE 1
  3. 3.++=
  4. 4.+=CODE 2
  5. 5.+=
  6. 6.−=CODE 3
  7. 7.−=
  8. 8.++=CODE 4
  9. 9.?+=12Which shape?
  10. 10.+?=9Which 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 vault.

Show answer key (for grown-ups)

Key: cross = 1 · moon = 8 · triangle = 7 · circle = 4

Every symbol is a whole number from 1 to 9.

1.circle + 26
2.11 - triangle4
3.triangle + moon + circle19
4.circle + triangle11
5.triangle + moon15
6.triangle - cross6
7.triangle - circle3
8.cross + circle + moon13
9.? + moon = 12circle
10.cross + ? = 9moon

Vault code: 4163

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 1 practices addition and subtraction within 20, and finding a missing shape. 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.

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