Bài 3:

a) 16.24:12

=16.(24:12)

=16.2

=32

b)270:3:5-4

=90:5-4

=18-4

=14

c)1000-930:31

=1000-30

=970

d)26.7-17.9+13.26-17.11

=(26.7+13.26)-(17.9+17.11)

=26.(7+13)-17.(9+11)

=26.20-17.20

=20.(26-17)

=20.9

=180

Bài 4:

$\left[\begin{array}{ccc}a&18&930&286&127\\b&6&30&22&12\\a.b&108&27900&6292&1524\\a:b&3&31&13&10\\0&0&0&0&7\end{array}\right]$ 

Bài 5:

a)48+253+52

=(48+52)+253

=100+253

=353

b)25.8.50.47.125.4.2

=(25.4).(50.2).(125.8).47

=100.100.1000.47

=470 000 000

c)18.72+29.18-18

=18.72+29.18-18.1

=18.(72+29-1)

=18.100

=1800

d)23.67+33.83+67.77+17.33

=(23.67+67.77)+(33.83+17.33)

=67.(23+77)+33.(83+17)

=67.100+33.100

=100.(67+33)

=100.100

=10 000

e)4.8.14+2.24.16+62.32

=32.14+32.24+62.32

=32.(14+24+62)

=32.100

=3 200

f)136.68+16.272

=136.68+16.2.136

=136.68+32.136

=136.(68+32)

=136.100

=13 600