How does the German method work?

25 * 65 = 1,625

25
65

5 * 5 = 25
(2 * 6) + 5 = 17
1,725 

What am I missing?

This only works with numbers both ending in 5, right? Change it to:

  35
x 79
---------
5 * 9 = 45
(3 * 7) + 9 = 30

3045 is ... incorrect. 🤨 

How do you get to the correct answer (2765) using German method?

Ah ok, found a video. You have to multiply all digits against each other and add anyway.
5*9=45
3*7=21 
(keep 2145 in mind)
now multiply the 5*7= 35, add it to the 3*9= 27, and then add those together (62) and add them to the middle two digits:

 2145
+_62_ 
_______
 2765

Corporate law, applied cryptography and other stuff.
https://paragraph.xyz/@avie


Ah ok, found a video. You have to multiply all digits against each other and add anyway.
5*9=45
3*7=21 
(keep 2145 in mind)
now multiply the 5*7= 35, add it to the 3*9= 27, and then add those together (62) and add them to the middle two digits:

 2145
+_62_ 
_______
 2765

https://www.youtube.com/watch?v=wP4vOS4SmYA