Pairs that make 10 are 1+9, 2+8, 3+7, 4+6
Eight counters were used. Counters 10 and 5 were not used.
Pairs that make 12 are 2+10, 3+9, 4+8, 5+7
Eight counters were used. Counters 1 and 6 were not used.
Pairs that make 13 are 3+10, 4+ 9, 5+8, 6+7
Eight counters were used. Counters 1 and 2 were not used.
Pairs that make 11 are 1+10, 2+9, 3+8, 4+7, 5+6
Ten counters were used. All counters were used.