If you used a random number generator for the numbers from 1 through 20 to play a game, what is the theoretical probability of getting each of these o

a:
Game:1
number of multiples of 3 or 7 from 1 to 20
total numbers $=20$
p(multiples of 3 or 7)=$(\text{no of multiples of 3 or 7)/(total numbers})$
$=8/20$
$=2/5$
b:
Game 1
Number of even or odd numbers$=20$
total numbers $=20$
p(even or odd)=$(\text{number of even or odd)/(total numbers})$
$=20/20$
$=1$
c:
no. of prime numbers and 1
total numbers $=20$
p(prime or 1)=$(\text{number of prime numbers or 1)/(total numbers})$
$=9/20$
d:
probability could be found by general probability which says
p(event)=$(\text{no.of times event occur)/(total no. of events})$
$=20/20$
$=1$
Result:
a: $2/5$
b: 1
c: $9/20$