Light reading and easy contest

[point]

Light reading:

https://steemit.com/education/@point/light-simple-and-strange-simple-math-to-play-with-win-1-sbd

Update and hint:

https://steemit.com/math/@point/contest-update-and-hint-the-moon-s-orbit-around-earth-makes-the-earth-wobble-how-much