1、56+31+24
=(56+24)+31
=80+31
=111,
2、615+475+125
=615+(475+125)
=615+600
=1215
3、125×64
=125×8×8
=1000×8
=8000
4、 89+101+111
=101+(89+111)
=101+200
=301
5、24+127+476+573
=(24+476)+(127+573)
=500+700
=1200
6、400-273-127
=400-(273+127)
=400-400
=0
7、327+(96-127)
=327-127+96
=200+96
=296
8、70×98
=70×(100-2)
=7000-140
=6860
9、442-103-142
=442-142-103
=300-103
=197
10、999+99+9
=1000+100+10-3
=1110-3
=1107
11、67×5×2
=67×(5×2)
=67×10
=670
12、25×(78×4)
=25×4×78
=100×78
=7800
13、72×125
=9×(8×125)
=9×1000
=9000
14、9000÷125÷8
=9000÷(125×8)
=9000÷1000
=9
15、400÷25
=400÷100×4
=4×4
=16
16、25×36
=25×4×9
=100×9
=900
17、103×27
=(100+3)×27
=2700+81
=2781
18、76×102
=76×(100+2)
=7600+152
=7752
19、3600÷25÷4
=3600÷(25×4)
=3600÷100
=36
20、99×35
=(100-1)×35
=3500-35
=3465
21、(25+12)×4
=25×4+12×4
1、56+31+24
=(56+24)+31
=80+31
=111,
2、615+475+125
=615+(475+125)
=615+600
=1215
3、125×64
=125×8×8
=1000×8
=8000
4、 89+101+111
=101+(89+111)
=101+200
=301
5、24+127+476+573
=(24+476)+(127+573)
=500+700
=1200
6、400-273-127
=400-(273+127)
=400-400
=0
7、327+(96-127)
=327-127+96
=200+96
=296
8、70×98
=70×(100-2)
=7000-140
=6860
9、442-103-142
=442-142-103
=300-103
=197
10、999+99+9
=1000+100+10-3
=1110-3
=1107
11、67×5×2
=67×(5×2)
=67×10
=670
12、25×(78×4)
=25×4×78
=100×78
=7800
13、72×125
=9×(8×125)
=9×1000
=9000
14、9000÷125÷8
=9000÷(125×8)
=9000÷1000
=9
15、400÷25
=400÷100×4
=4×4
=16
16、25×36
=25×4×9
=100×9
=900
17、103×27
=(100+3)×27
=2700+81
=2781
18、76×102
=76×(100+2)
=7600+152
=7752
19、3600÷25÷4
=3600÷(25×4)
=3600÷100
=36
20、99×35
=(100-1)×35
=3500-35
=3465
21、(25+12)×4
=25×4+12×4