Simple Probability problem

Question

A box contains papers numbered 1 to 8. Two slips are drawn, one after the other without replacement.

a) What is the probability that both numbers are even? (and for my sake why)

b) The first number drawn is a five and the second is composite? (a small explanation)

Answer 1

The probability that the first slip is even is 1/2

 

The odd the second one is even given the.first is even is 3/7

 

Therefore the odds of picking 2 evens is 1/2 x 3/7 = 3/14

 

b) The chance that 5 is picked on the first slip is 1/8

The odds that the second slip is composite given that the first number is a 5 is 3/7

1/8 x 3/7 = 3/56

composite numbers have factors other than 1 and itself Of the numbers 1-8, : 4,6,8 are composite