Question

A single die is rolled. Find the probability of rolling an even number or a number less than 6.

Answer 1

3/6=1/2 for even number
number less than 6 is 5/6?

Answer 2

3/6+5/6?

Answer 3

remember to subtract the overlap. ;-)

Answer 4

overlap of 2/6? is that right?

Answer 5

Right, because 3/6+5/6 > 1 and probabilities can't be greater than 1.

Answer 6

But you could also just think of the actual situation. Is it ever possible to roll a number on a die that wasn't less than six and not even?

Answer 7

8/6 - 2/6

Answer 8

1? Sorry lol was looking for my calculator LOL!

Answer 9

If you don't roll a number less than 6, then you've rolled a 6, and 6 is even.
Consider the sample space!

Answer 10

*smh* Put. The. Calculator. Down. :-p

Answer 11

LOL! it's 3/6+5/6-2/6 right?

Answer 12

Yes, that's using the formula. It's called the addition rule.
P(A ∪ B) = P(A) + P(B) - P(A ∩ B))

Answer 13

so the answer is 1?

Answer 14

But it's impossible to roll a die and not get one of those possibilities, so no calculation is necessary.

Answer 15

huh? im confused!

Answer 16

I posted this in response to your other question:
Check it out:
http://stattrek.com/probability/probability-rules.aspx?Tutorial=Stat

Answer 17

Think of the sample space: possibility one = a number less than 6. possibility two = an even number. If it is not a number less than 6, then it is 6 and 6 is an even number. No matter how you roll the die, there is a 100% chance of one of those things happening!

Answer 18

so there is a 100% chance of rolling an even number or getting a number less than 6?

Answer 19

How about this: The probability of it raining is .4, the probability of it not raining is .6. What is the probability of it raining and not raining at the same time?
You don't need to calculate anything; they are mutually exclusive events, so the probability is automatically zero!

Answer 20

so, it's 0 not 1?

Answer 21

That's a different example. Ignore that for now.

Answer 22

oh goodness... im so lost

Answer 23

Oh dear.. I'm just asking you to think about the situation logically to avoid needless computation.

Answer 24

But, see I'd calculate it rather then thinking logically ;p

Answer 25

thinking logically with me doesn't work out... (obviously)

Answer 26

So the answer is 1,100%, 6/6? right lol any of those

Answer 27

Do you have a real, actual six-sided die handy? If not, can you imagine holding one in your hand and looking at it?
Look at (or imagine looking at) all the faces. Do you see that no matter which face you look at, it is either a number less than six or it is six itself? Six is an even number, so every roll of the die falls into one of those categories.
Save the calculations for the complicated situations, something like this can be answered in a snap with no work at all.

Answer 28

*sigh* alright, just keep the formulas handy then and know when to use a particular one.

Answer 29

Lol, I get what you said in the previous comment^ the others... completely confused me though:)