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CRACK THE CODE · GRADE 1

Robo-Decoder Challenge

Use your addition and subtraction skills to find the number value of each robot part so you can open the locked storage trunk.

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

=9
=1
=8
=2

Every symbol is a whole number from 1 to 9.

Crack these

  1. 1.20−=
  2. 2.++=CODE 1
  3. 3.+2=
  4. 4.+=CODE 2
  5. 5.+=
  6. 6.−=CODE 3
  7. 7.++=
  8. 8.+3=CODE 4
  9. 9.?+=10Which shape?
  10. 10.?+=10Which 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 locked storage trunk.

Show answer key (for grown-ups)

Key: cross = 9 · square = 1 · ring = 8 · triangle = 2

Every symbol is a whole number from 1 to 9.

1.20 - ring12
2.cross + ring + square18
3.cross + 211
4.triangle + cross11
5.triangle + ring10
6.ring - triangle6
7.triangle + cross + square12
8.ring + 311
9.? + square = 10cross
10.? + ring = 10triangle

Vault code: 8161

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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