Use what you know about place value to write it as

0.16 = 16/100

Then, reduce the fraction in the usual way.

16/100 = (4*4)/(4*25) = (4/25)*(4/4)

0.16 = 16/100

Then, reduce the fraction in the usual way.

16/100 = (4*4)/(4*25) = (4/25)*(4/4)

**= 4/25**