Question

A box contains card numbered 1 to 20 .A card is drawn at random fromthe box . Find the probability that number on the drawn card is a prime number a composite number a number divisibleby 3

Answer 1

Answer:

P(a prime number is drawn) = 2 / 5

P(a composite number is drawn) = 11 / 20

P(a number divisible by 3 is drawn) = 3 / 10

Step-by-step explanation:

The prime numbers from 1 to 20 are:  2, 3, 5, 7, 11, 13, 17, 19.

There are 8 of them.  So...

P(a prime number is drawn)

= ( # ways of getting a prime number ) / ( # ways of drawing a card )

= 8 / 20

= 2 / 5

The composite numbers from 1 to 20 are those that are not prime and not 1.  So there are 20 - 8 - 1 = 11 of them.  [ Alternatively, we could just list them like we did with primes and then count them:  4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20.  Yep... 11 of them. ]  So...

P(a composite number is drawn)

= ( # ways of getting a composite number ) / ( # ways of drawing a card )

= 11 / 20

The multiples of 3 from 1 to 20 are:  3, 6, 9, 12, 15, 18.

There are 6 of them.  So...

P(a number divisible by 3 is drawn)

= ( # ways of getting a multiple of 3 ) / ( # ways of drawing a card )

= 6 / 20

= 3 / 10

Answer 2

Answer:

Step-by-step explanation:

total number of outcomes=20

1. favourable outcomes=8

probability of getting a prime number=8/20=2/5

2. favourable outcomes =11

probability of getting a composite numer=11/20

3.favourable outcomes =6

probability getting a multiple of 3=6/20=3/10

hope it helped ^_