10.
10.
Between them they are all the integers from 30 to 50.
33,35,39,45,49
50
50
33, 35, 39, 45, 49
50 of them.
25.
25
31 37 41 43 47
half of (50 - 20)
450... There are 500 odd numbers from 000 to 999 inclusive. From 000 to 099, there are 50 odd numbers. 500 - 50 = 450.