At this point we re-design the cards and holders. Instead of a patterned back to the cards we have the negative of the number. One side of a holder also shows the negative of the other.
So flipping gives and vice versa.
Flipping gives and vice versa.
Flipping over gives and vice versa.
(Not so new really as the rule has always been – instead of removing cards add their negative, now we are just applying this in bulk.)
Whenever there is a negative holder flip the holder and the cards.
Now when you have the hand flip the negative holder to give
and give the same result of twenty black counters, the number Twenty.
Recording 5 x 4 = (-5) x (-4) = 20
and give the same result of twenty white counters, the number Negative Twenty.
Recording 5 x (-4) = (-5) x 4 = (-20).