What is the probability that the ticket drawn has a number which is a multiple of 3 or 7 ?

Question

Ticket numbered from 1 to 20 are mixed up and a ticket is drawn at random.
What is the probability that the ticket drawn has a number which is a multiple of 3 or 7 ?

Answer 1

multiples of 3
3 6 9 12 15 18

multiples of 7
7 14

all possible outcomes 6+2=8

probability= 8/20
=2/5

Answer 2

From 1 to 20 numbers divisible by 3 are 6 by 7 are 2.
So, favourable outcomes are 8 out of a possible 20 outcomes
Probability = favourable outcomes / possible outcomes
= 8/20 = 2/5 = 0.4

Answer 3

p(E) = 8c1 / 20c1 = 8/20.....

multiples of 3= 3 , 6 , 9 , 12 ,15 , 18..

multiples of 7 = 7 , 14,,,,,