Question

tính nhanh: b,6x1235x20-5x235x24

                   c,(145x99+145)-143x101-143

 

                    d,54x47-47x53-20-27

Answer 1

`#040911`

`b,`

`6 \times 1235 \times 20 - 5 \times 235 \times 24`

`= 6 \times (1000 + 235) \times 20 - 5 \times 235 \times 24`

`= 120 \times 1000 + 120 \times 235 - 120 \times 235`

`= 120 \times 1000 + 0`

`= 120000`

`c,`

\((145 \times 99+145)-143 \times 101-143\)

`=`\(145 \times 99 + 145 - 143 \times 101 - 143\)

`=`\(145 \times (99 + 1) - 143 \times (101 - 1)\)

`=`\(145 \times 100 - 143 \times 100\)

`=`\(100 \times (145 - 143)\)

`=`\(100 \times 2=200\)

`d,`

`54 \times 47 - 47 \times 53 - 20 - 27`

`= 54 \times 47 - 47 \times 53 - (20 + 27)`

`= 54 \times 47 - 47 \times 53 - 47`

`= 47 \times (54 - 53 - 1)`

`= 47 \times 0=0`