Basically, take the numbers 1/3, -1/3, and count how many terms you need to produce something that sums to a whole number. You can get four with (1/3 + 1/3 - 1/3 - 1/3), so it's not an impossible configuration.
> Basically, take the numbers 1/3, -1/3, and count how many terms you need to produce something that sums to a whole number.
Shouldn't there be +2/3 and -2/3 charges as well? Otherwise the only way to do this is with an equal number of +1/3 and -1/3 charges (so not 5 total, for example).
You can get five with (1/3 + 1/3 + 1/3 + 1/3 - 1/3). Note that I'm not really talking about charges directly so they don't need to be equal, but rather I'm using these numbers as a proxy for charges. So this configuration might be something like (red, green, blue, red, antired).
It's just a quick rule for showing how many quarks can fit together, not what kinds of quarks they are.
Any whole number of terms greater than 1 will allow this, by the way.