The whole bar is every ball in the bag — the event slice plus the "not event" slice always fills it.
Chase:
A red ball
A gold ball
A green ball
↻ New bag
P(red)
3/8
P(not red)
5/8
P(red) + P(not red)
1
3/8
+
5/8
=
8/8 = 1
Pick a colour to chase. The
brass slice
is your event; the
mustard slice
is
everything that isn't
. Together they always fill the whole bar — so the two chances always add to
1
.