3 ms·

I think its advantage is reliability. I don't know if it does much for speed. You can't make off by 1 or 2 errors because then you'd end up with a count like 2

I think its advantage is reliability. I don't know if it does much for speed. You can't make off by 1 or 2 errors because then you'd end up with a count like 23 or 27. You're counting by 5... the last digit needs to be 0 or 5! And you're not going to make an off by 10 error. You can visually pick out 2s and 3s to make your 5 before you add them in.

jolmg 8y ago
In my experience, you can make off by 1 or 2 errors when you accidently include 1 or 2 items in different groups of 5 at the same time. You end up with 25 when you should have ended up with 23. It may also happen that you don't include 1 or 2 items in the groups, because you thought you'd already included them, while visually scanning the area. When that happens, you end up with 25 when you should have ended with 27.