Question

How would you convince someone that 0.57 is a rational number?

Answer 1

A rational number, by definition, is a number that can be shown in fractional form.

0.57 can be shown in fractional form, as 57/100.

Answer 2

I would show him that it can be written as. 57/100.

Then I would tell him that EVERY number that can be completely written down with digits is a rational number.