Hey there,
A method I use a lot which works for generally more simple calculations: breaking down divisions into simpler parts. The key principle here is that it's easier to divide by small numbers - 2, 3, 5, 10.
The easiest is when the number you are dividing by is a square of two (4, 8, 16 ,32, etc.)
520 / 8 = 520 / (2 x 2 x 2) - so now, you just divide by 2 three times! 520, 260, 130
You can also do the same with dividing by 3.
380 / 6 = 380 / (2*3) = 190/3. Now to figure this out, find the closest multiple of three basically throuhg quick trial and error in your head. In this case, it's 180 = 3*60. if 180/3=60, then 190/3 is 60+(10/3), or 63.33
Finally, a tip to divide by 5: I always think of dividing by 5 as dividing by 10, multiplying by 2 (because 5=10/2). So for example:
740 / 5 = 740/(10)*2 = 74*2 =148.
This last trick with 50s of course also works with 50, 500, etc.
Hope this helps!