### The basics

Arithmo–Missing is very similar to all the other Arithmo games in that it uses the basic math functions: addition, subtraction, multiplication, and division. Several people can play at the same time. The person to solve their puzzle first wins!

In Arithmo–Missing you’re given a grid size, 2x2, 2x3, or 3x3, filled with numbers.. The object is to connect 3 adjacent numbers into equations to make a product from 13 to 24. We call these products Equa-13, Equa-14, Equa-15, and so on. Equa-15, for example, simply means "any three adjacent connected numbers on the grid that together can be made to equal 15."

Remember that in the Arithmo world, "3 Connected Numbers" always means any 3 adjacent numbers on the grid that you can directly connect using a straight vertical, horizontal, or "L" shaped line. Once you connect 3 numbers, you add, subtract, multiply, or divide them together in any order or combination to make a product.

Each grid in the Senior version of Missing! allows you to make connections and equations to come up with the various Equa-13 to Equa-24 products. However, you’ll find that in each Arithmo–Missing! puzzle, you won’t be able to make one or more of the Equa equations. Your mission is to figure out which equation you can’t make!

### Rules of the Game

On your number filled grid, it is possible to make equations and connections of 3 adjacent numbers and make them equal a number from 13 to 24. We call these products Equa-13 to Equa-24. However, one or more of the Equas are missing. Your goal is to figure out which products you cannot make. Since you don’t know which ones are missing, you’ll have to make connections and find all of the Equas that do exist, until you can point out the ones that don’t.

It’s simple: let’s use a basic example.

You have a grid with numbers in it. You start forming connections of 3 adjacent numbers and make them equal a number from 13 to 24 using the four basic math operations however you want. But you’ll run into a problem: you’ll eventually realize that no matter what you do, you can’t make any of the connections and equations you come up with equal 15 (or any other number from 13 to 24). You might have found 13,14,16,17, and the others, but you can’t make an equation that equals 15! That means that Equa-15 is the missing equation, and you found it! Good work!

Again, when we say "connections", "Equas", or "equations", we mean 3 adjacent numbers on the grid you can directly connect in a straight horizontal, vertical, or "L" shaped line and add, subtract, multiply, or divide together in any order or combination to equal from 13 to 24.

### Example

Your Task: 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 8x8:4=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 11x8:4=22, Equa-23 11+8+4=23, Equa-24 8x(8-5)=24

You can see that no matter how hard you try, one equation simply cannot be made no matter what math you do. Equa-19 can not 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 Arithmo–Missing game is: One Equa is missing, and that is Equa-19. That wasn’t too bad, right? Go find more missing Equas, and enjoy!

### Skill Levels

Arithmo–Missing tasks are divided into 3 skill levels: Easy, Medium, Difficult.