1.Tính nhẩm :
\[1 \times 2 = .......\] \[1 \times 3 = .......\] \[1 \times 4 = .......\] \[1 \times 5 = .......\]
\[1 \times 1 = .......\] \[2 \times 1 = .......\] \[3 \times 1 = .......\] \[4 \times 1 = .......\]
\[5 \times 1 = .......\] \[1:1 = .......\] \[2:1 = .......\] \[3:1 = .......\] \[4:1 = .......\] \[5:1 = .......\]
2.Số ?
3.Tính
a]
\[\eqalign{ & 2 \times 3 \times 1 = ................ \cr & {\rm{ = }}................. \cr} \] \[\eqalign{ & 2 \times 1 \times 3 = ................ \cr & {\rm{ = }}................. \cr} \]
b]
\[\eqalign{ & 4 \times 5:1 = ................ \cr & {\rm{ = }}................. \cr} \] \[\eqalign{ & 4:1 \times 5 = ................ \cr & {\rm{ = }}................. \cr} \]
c]
\[\eqalign{ & 8:4 \times 1 = ................ \cr & {\rm{ = }}................. \cr} \] \[\eqalign{ & 8 \times 1:4 = ................ \cr & {\rm{ = }}................. \cr} \]
d]
\[\eqalign{ & 12:3:1 = ................ \cr & {\rm{ = }}................. \cr} \] \[\eqalign{ & 12:1:3 = ................ \cr & {\rm{ = }}................. \cr} \]
Giải
1.Tính nhẩm :
\[1 \times 2 = 2\] \[1 \times 3 = 3\]
\[1 \times 4 = 4\] \[1 \times 5 = 5\]
\[1 \times 1 = 1\] \[2 \times 1 = 2\]
\[3 \times 1 = 3\] \[4 \times 1 = 4\]
\[5 \times 1 = 5\] \[1:1 = 1\] \[2:1 = 2\]
\[3:1 = 3\] \[4:1 = 4\] \[5:1 = 5\]
2.Số ?
3.Tính
a]
\[\eqalign{ & 2 \times 3 \times 1 = 6 \times 1 \cr & {\rm{ = 6}} \cr} \] \[\eqalign{ & 2 \times 1 \times 3 = 2 \times 3 \cr & {\rm{ = 6}} \cr} \]
b]
\[\eqalign{ & 4 \times 5:1 = 20:1 \cr & {\rm{ = 20}} \cr} \] \[\eqalign{ & 4:1 \times 5 = 4 \times 5 \cr & {\rm{ = 20}} \cr} \]
c]
\[\eqalign{ & 8:4 \times 1 = 2 \times 1 \cr & {\rm{ = 2}} \cr} \] \[\eqalign{ & 8 \times 1:4 = 8:4 \cr & {\rm{ = 2}} \cr} \]
d]
\[\eqalign{ & 12:3:1 = 4:1 \cr & {\rm{ = 4}} \cr} \] \[\eqalign{ & 12:1:3 = 12:3 \cr & {\rm{ = 4}} \cr} \]