Numbers have gone missing. Only a math sleuth can find them.

Object of the Game

In this game, one, two, or three Equas between 13 and 24 CANNOT be made when you calculate any three adjacent number combinations. Your goal is to figure out which are the missing Equas.

How to Play

  • Select a 2×2, 2×3, or 3×3 grid size.
  • Missing is a process of elimination. Since you do not know which Equas are missing, you will have to make calculations to find all of the Equas between 13 and 24 that do exist, before you can find the ones that don’t.
  • In this puzzle, adjacent numbers are three numbers connected vertically, horizontally or in an “L” shape, as shown in the diagrams below:

Horizontal equa
Vertical equa
L-shaped Equa

  • Missing is very similar to all the other Arithmo games in that it uses the basic math functions: addition, subtraction, multiplication, and division.
  • Use only basic arithmetic functions: addition, subtraction, multiplication, division; and follow the order of operations when necessary.


Find which Equas, from 13 to 24, are missing on the grid.


As you can see, we can make the following equations using the following connections:

  • Equa-13 11+(8:4)=13,
  • Equa-14 8+5+1=14,
  • Equa-15 8+8-1=15,
  • Equa-16 8×8:4=16,
  • Equa-17 8+8+1=17,
  • Equa-18 5+5+8=18,
  • Equa-20 4+8+8=20,
  • Equa-21 8+8+5=21,
  • Equa-22 11×8:4=22,
  • Equa-23 11+8+4=23,
  • Equa-24 8x(8-5)=24

However, Equa-19 cannot be found on this grid. No matter which three adjacent numbers you connect, you will never be able to make them equal 19.

The solution for this puzzle is that only one Equa is missing, and that is Equa-19.

That was easy, right?  So now it’s time to dive in and go “missing” for awhile.

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