Why does this work?

Question

https://code.sololearn.com/c4zqu5sVICTd/?ref=app

In order to calculate the hex value, I have to divide the rgb code numbers by 16 for the first hex number/letter, then take the remainder and multiply by 16 for the second. (Full explanation through website in code)

So, my guess for the second number/letter was (rgb%16)*16. But in code this doesn't work and it's only rgb%16. Why?

Answer 1

Compare how you would get digits from a 2-digit number in base 10.

Given 65 as the number:
left digit = (int) 65/10 = 6
right digit = 65%10 = 5

You wouldn't multiply 5*10 afterward.

Understand that the modulo operator evaluates to the integer remainder after whole number division. It is equivalent to 65 - (int)(65/10)*10 = 5.