nhanh ạ đag cần gấp
Bài `1`
\(a,27+123+73+7+140\)
\(=\left(27+73\right)+\left(123+7\right)+140\)
\(=100+130+140\)
\(=230+140\)
\(=370\)
\(b,117+83+553+47\)
\(=\left(117+83\right)+\left(553+47\right)\)
\(=200+600\)
\(=800\)
\(c,7654321-999998\)
\(=7654321-\left(100000-2\right)\)
\(=7654321-100000+2\)
\(=7554321+2\)
\(=7554323\)
\(d,7543-1995\)
\(=7543-\left(2000-5\right)\)
\(=7543-2000+5\)
\(=5543+5\)
\(=5548\)
Bài `2`
`a, 4*86*25`
`= (4*25)*86`
`= 100*86`
`= 8600`
`b,(1800-144)÷36`
`= 1800 ÷ 36 - 144 ÷ 36`
`= 50 - 4`
`= 46`
`c, 38*25 + 75*38 - 280`
`= (75 + 25)*38 - 280`
`= 100*38 - 280`
`= 3800 - 280`
`= 3520`
`d, 26*18 - 13*26`
`= 26*(18-13)`
` = 26*5`
`= 130`
Dạng 2:
Bài 1 :
\(a,75+4\cdot23-3\cdot52\)
\(=75+92-156\)
\(=167-156\)
\(=11\)
\(b,2\cdot52+210:70-54:27\)
\(=104+3-2\)
\(=107-2\)
\(=105\)
Bài 2 :
\(a,12:\left\{400:\left[500-\left(125+25\cdot7\right)\right]\right\}\)
\(=12:\left\{400:\left[500-\left(125+175\right)\right]\right\}\)
\(=12:\left\{400:\left[500-300\right]\right\}\)
\(=12:\left\{400:200\right\}\)
\(=12:2\)
\(=6\)
\(b,135-\left[150-\left(23\cdot10-23\cdot5\right)\right]\)
\(=135-\left[150-23\cdot\left(10-5\right)\right]\)
\(=135-\left[150-23\cdot5\right]\)
\(=135-\left[150-115\right]\)
\(=135-35\)
\(=100\)
