Brain Tease.. Some of you may have seen this as I did pick it up on the net, but I thought that it was a pretty good logic test so I will post and see how long it takes to get the...

Blurryeyed Loc: NC Mountains.

Some of you may have seen this as I did pick it up on the net, but I thought that it was a pretty good logic test so I will post and see how long it takes to get the right answer preferably from someone who has not seen it posted elsewhere...

A die is rolled and then a coin is flipped, what are the probabilities of flipping a tail, and then rolling an odd number?

This came from a HS math quiz.

tschmath Loc: Los Angeles

Blurryeyed wrote:

Some of you may have seen this as I did pick it up on the net, but I thought that it was a pretty good logic test so I will post and see how long it takes to get the right answer preferably from someone who has not seen it posted elsewhere...

A die is rolled and then a coin is flipped, what are the probabilities of flipping a tail, and then rolling an odd number?

This came from a HS math quiz.

P(t) = 1/2
P(odd) = 3/6 = 1/2

P(t,odd) = (1/2) x (1/2) = 1/4

tschmath Loc: Los Angeles

Blurryeyed wrote:

Some of you may have seen this as I did pick it up on the net, but I thought that it was a pretty good logic test so I will post and see how long it takes to get the right answer preferably from someone who has not seen it posted elsewhere...

A die is rolled and then a coin is flipped, what are the probabilities of flipping a tail, and then rolling an odd number?

This came from a HS math quiz.

P(t) = 1/2
P(odd) = 3/6 = 1/2

P(t,odd) = (1/2) x (1/2) = 1/4

Blurryeyed Loc: NC Mountains.

tschmath wrote:

quote=Blurryeyed Some of you may have seen this a... (show quote)

That is what I would have said but it was not the answer offered and in this case I agree that it is incorrect.

tschmath Loc: Los Angeles

Blurryeyed wrote:

quote=tschmath quote=Blurryeyed Some of you may ... (show quote)

I'd be curious as to the answer, because if you list all the possible outcomes there are 12, and only three of them have a tail and an odd number. Looks like someone screwed up when they came up with the answer.

Blurryeyed Loc: NC Mountains.

tschmath wrote:

quote=Blurryeyed quote=tschmath quote=Blurryeye... (show quote)

I am not so sure that many people are interested in this tease tschmath and I know that you love and excel at these, so I will give you a tidbit that might help... Don't think of it as a math question....

Blurryeyed Loc: NC Mountains.

Well Tschmath this tease is not gaining any traction and I am sure that you have probably figured this out... the student viewed this question as a logic question and answered that the probability was 0% because the die was rolled before the coin was flipped...

I do not see how you can fault his logic.

tschmath Loc: Los Angeles

Blurryeyed wrote:

Well Tschmath this tease is not gaining any traction and I am sure that you have probably figured this out... the student viewed this question as a logic question and answered that the probability was 0% because the die was rolled before the coin was flipped...

I do not see how you can fault his logic.

Because the two events a independent of each other. The order makes no difference. The thing I noticed in your original post was the word probabilities instead of probability, in which case there were two answers, as I showed in my answer. But the order of the flip/roll is irrelevant, just as multiplication is commutative. I stand by my answer.

Blurryeyed Loc: NC Mountains.

Tschmath, your math for solving probability is correct, there is no argument there, and you are right that I should have used the singular I don't proof read my posts and often have typos and misused words, but the logic remains if you roll the die and then flip the coin what is the probability of flipping a tail and rolling an odd... I had posed the question from memory... So it is not posted exactly as it appeared on the quiz/exam.. I thought that I had pretty much worded it similarly as far as if this then that, but I did word it differently, If it is a singular event then the probability is zero as the die was rolled before flipping the coin, if they are independent events then it is 1:4 as you demonstrated.

Here is the original post I came across online, I was really just posting this for fun as when I saw it I too solved it for the math and then had to admire the student's logic...

Anyway, this post was supposed to be more of a fun gotcha puzzle than a math problem.

Kombiguy Loc: Cedar Rapids, IA

Clever. The question is worded incorrectly, so the student's answer is exactly right.

Wellhiem Loc: Sunny England.

Blurryeyed wrote:

Some of you may have seen this as I did pick it up on the net, but I thought that it was a pretty good logic test so I will post and see how long it takes to get the right answer preferably from someone who has not seen it posted elsewhere...

A die is rolled and then a coin is flipped, what are the probabilities of flipping a tail, and then rolling an odd number?

This came from a HS math quiz.

Part 1: A die is rolled and then a coin is flipped.
Part 2: What are the probabilities of flipping a tail, and then rolling an odd number?
At no point is it stated that part 1 and part 2 are the same instance.
Therefore the answer to part 2 is 0.25. Part 1 is an irrelevance.

Kombiguy Loc: Cedar Rapids, IA

Wellhiem wrote:

quote=Blurryeyed Some of you may have seen this a... (show quote)

I would agree, except that it was all in one sentence. One is entitled to read the sentence as written, and answer the question as asked.
D then C, what are the odds of C then D? The answer to the question asked is 0.
This is why math teachers need to be fluent in English.

winterrose Loc: Kyneton, Victoria, Australia

I think it is commonly referred to as R.T.F.Q.....

DRC56 Loc: Sartell, MN

1/2, they are independent. if you flip the coin then 50% chance of flipping tails. If you get tails then you have a 50% chance of rolling an odd number

Blurryeyed Loc: NC Mountains.

DRC56 wrote:

1/2, they are independent. if you flip the coin then 50% chance of flipping tails. If you get tails then you have a 50% chance of rolling an odd number

Tschmath was right in calculating the probability of the outcomes if you do not consider ill fated logic of the question, for the event there are four possible outcomes and you are calculating the probability of the occurrence of just one of those outcomes... ie

Heads/even
Heads/odd
Tails/even
Tails/odd...

I posted this because if you read the question as posed on the test I think that it certainly can be argued that the student's answer was correct.