\(28\times78+28\times22\\ =28\times\left(78+22\right)\\ =28\times100\\ =2800\)
~~~~~~~~~~~~~~~~~~
\(75\times27+75\times72+75\\=75\times\left(27+72+1\right)\\ =75\times100\\ =7500\)
~~~~~~~~~~~~~~~~~~
\(8064:64\times37\\ =126\times37\\ =4662\)
`28 xx 78 + 28 xx 22`
`= 28 xx ( 78+22)`
`=28xx100`
`=2800`
____________________
`75 xx 27 + 75 xx 72 + 75`
`= 75 xx 27 + 75 xx 72 + 75xx1`
`=75xx(27+72+1)`
`=75xx100`
`=7500`
______________________________
`8064 : 64 xx 37`
`=126xx37`
`=4662`
______________________________
`12 : { 390 : [ 500 - ( 125 + 35 - 7)]}`
`=12 : { 390 : [ 500 - ( 160 - 7 )]}`
`=12 : { 390 : [ 500 - 153]`
`=12 : { 390 : 347}`
`=12 : 390/347`
`=12 xx 347/390`
`=694/65`
28 ×78+28 ×22=\(28x\left(78+22\right)=28x100=2800\)
75 × 27+75 ×72+75=\(75x\left(27+72+1\right)=75x100=7500\)
8064:64 ×37\(=126x37=126x\left(40-3\right)=126x40-126x3\)
\(=5040-378=4662\)
12:{390:[500-(125+35-7)]}
\(=12:\left\{390:\left[500-\left(160-7\right)\right]\right\}\)
\(=12:\left\{390:\left[500-153\right]\right\}\)
\(=12:\left\{390:347\right\}\)
\(=12:\dfrac{390}{347}=12x\dfrac{347}{390}=\dfrac{12x347}{390}=\dfrac{6x2x347}{6x65}=\dfrac{694}{65}\)( chả bt sau đề ko mà số hơi lớn)
\(=\)\(28 ×78+28 ×22\)
\(=\)\(28 ×(78+22 )\)
\(=\)\(28 ×100=2800\)
\(-----------\)
\(75 × 27+75 ×72+75\)
\(=75 ×( 27+72+1)\)
\(=75 ×100=7500\)
\(-----------\)
\(8064:64 ×37\)
\( = 126 x 37\)
\(= 4662\)
\(------------\)
12:{390:[500-(125+35-7)]}
12 : { 390 : [ 500 - { 125 + 245 } ]
12 : { 390 : [ 500 - 370 ] }
12 : { 390 : 130 }
12 : 3=4