30. a)$\frac{17}{40}$ =$\frac{425}{1000}$ =0,425
b) $\frac{321}{320}$ =1,003125
c) $\frac{1}{64}$ =0,015625
d)$\frac{1}{625}$ =$\frac{16}{10000}$ =0,0016
31. a)1,32=1$\frac{8}{25}$ =$\frac{33}{25}$
b) 0,625=$\frac{625}{10000}$ =$\frac{1}{16}$
c) 3,128=3$\frac{128}{1000}$ =3$\frac{16}{125}$ =$\frac{391}{125}$
d) 25,25=25$\frac{25}{100}$ =25$\frac{1}{4}$ =$\frac{101}{25}$