I came across this little puzzle in play store and would like to recommend it. The puzzle is quite simple, you are given four numbers and you need to work out a way to make them equal 10 using +, -, x, / or ().

There are 500 puzzles to solve. They all have the same format, the four numbers are presented, you can drag them into a different order and drag the mathematical operators between the number. When all four numbers are used you get the total, and if that’s 10 you can move on. Some screenshots are shown below.

I liked the simple premise and the simple design. The app is programed by Sveinn Steinarsson. The puzzle is inspired by a mind game described by Ewa Anna Dwornik.

I enjoyed the questions this puzzle raised in my mind. The first one was how many unique sets of four digits are there. It did not take me long to work out there are 715. This explained why there are 500 levels in the puzzle as there will be some sets of numbers where you cant make 10, 0-0-0-0 for example.

Question 2, how many of the 715 combinations are solvable? A quick python script to run through all sets gives us 552 as solvable.

What about other target numbers? A target of 12, 544 of 715 are solvable. A target of 20, 433 are solvable and a target of 0, gives 705 as solvable.

The makers of the app also spotted this and you can purchase add on level for different targets. I think I will try these.

Artistic Ratings

The ratings I have chosen for this puzzle is 4,7,8. The art element is not that high with this puzzle but I do like the simple aesthetic of the way the puzzle is presented. The design is strong with solid bug free programming. The simplicity of the puzzle adds to its design and it get a couple of bonus points for being ad free.

Puzzle Category:
Puzzle Top Level
--- Mobile Puzzle

Artistic Ratings
  • Artistic: 4
  • Aesthetic: 7
  • Design: 8