Hello good people,
as a math nerd I like creating number enigmas. Wanna solve some? But note that the enigmas are not copied from other sources! So some might be too easy, some might be too difficult, and some might not have a unique answer. Plz don't use any computer programs to solve it. Thx
The first post with the right answer gets my upvote (and comment). I encourage other users to upvote the corresponding solution as well. Have fun and feel free to give critique, feedback and stuff.
Greetings Schneidor
Enigma:
What is the missing number and how to compute?
[1; 3; 7; 15; 13; 9; 19; 21; *; 15]
