（ただし１と２を合せて１２のような使い方は出来ません。）
55個の解法が見つかりました。
(((4+9)-2)-1)=10
((1×2)×(9-4))=10
((2×(9-4))÷1)=10
((2÷1)×(9-4))=10
((4+(9-1))-2)=10
((4+(9-2))-1)=10
((4+9)-(1+2))=10
((4-(1-9))-2)=10
((4-(2-9))-1)=10
((4-1)+(9-2))=10
((4-1)-(2-9))=10
((4-2)+(9-1))=10
((4-2)-(1-9))=10
((4÷2)+(9-1))=10
((4÷2)-(1-9))=10
((9+(4-1))-2)=10
((9+(4-2))-1)=10
((9+(4÷2))-1)=10
((9-(1-4))-2)=10
((9-(2-4))-1)=10
((9-1)+(4-2))=10
((9-1)+(4÷2))=10
((9-1)-(2-4))=10
((9-2)+(4-1))=10
((9-2)-(1-4))=10
((9-4)×(1×2))=10
((9-4)×(2÷1))=10
((9-4)÷(1÷2))=10
(1×(2×(9-4)))=10
(2×((1×9)-4))=10
(2×((9-4)÷1))=10
(2×((9÷1)-4))=10
(2×(1×(9-4)))=10
(2×(9-(1×4)))=10
(2×(9-(4÷1)))=10
(2÷(1÷(9-4)))=10
(4+((9-1)-2))=10
(4+((9-2)-1))=10
(4+(9-(1+2)))=10
(4-((1+2)-9))=10
(4-(1+(2-9)))=10
(4-(1-(9-2)))=10
(4-(2+(1-9)))=10
(4-(2-(9-1)))=10
(9+((4-1)-2))=10
(9+((4-2)-1))=10
(9+((4÷2)-1))=10
(9+(4-(1+2)))=10
(9-((1+2)-4))=10
(9-(1+(2-4)))=10
(9-(1-(4-2)))=10
(9-(1-(4÷2)))=10
(9-(2+(1-4)))=10
(9-(2-(4-1)))=10