Câu 1, 2, 3, 4 Vở bài tập toán 2 tập 2 Trang 48

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)

\(\eqalign{  & 12:3:1 = 4:1  \cr  & {\rm{             = 4}} \cr} \)                 \(\eqalign{  & 12:1:3 = 12:3  \cr  & {\rm{             = 4}} \cr} \)

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