In a single roll of a six-sided dice, what is the probability of rolling a three or an even number?

2 Answers
Oct 15, 2017

1/12

Explanation:

You have 2 events: A & B.
color(magenta)A: rolling a three
color(blue)B: rolling an even number

rArr P(A and B)=P(A)*P(B)

Probability of rolling a three color(magenta)Ararr 1/6
Probability of rolling an even number color(blue)B: you either get a 2,4 or 6. rarr 3/6

P(A)*P(B)=1/6*3/6
=1/12

Oct 17, 2017

color(blue)(2/3)

Explanation:

We have two events A and B:

A being an even number 2 4 6.
B being a 3.

P(A) = 3/6=1/2

P(B)= 1/6

Since this is an A or B event occurring, we have a union of events. i.e. AuuB. This strictly means A or B or both. In this particular case A and B cannot occur simultaneously since they are mutually exclusive events. You can't throw a 3 and an even number, since 3 is an odd number.

So we have:

P(A or B) = P(A) + P(B)=> 1/2+1/6= 4/6 =color(blue)(2/3)

We could have obtained this result directly by considering the 2 events as one event:

An even number and 3 is four favourable outcomes, so:

4/6=color(blue)(2/3)