1 to 50*** has 50 numbers, of which 25 are odd and 25 are even. So the probability of drawing an odd number or an even number is 25/50 = 1/2.

If we think that 1~25 is a small number and the rest is a big number, then * * * has 25 small numbers and 25 big numbers, and the probability of drawing small numbers and big numbers is also 25/50 = 1/2.