BrainDen.com - Brain Teasers
• 0

## Question

I heard this on Leno last night and thought it made a decent teaser.

A new energy company does a survey on how many people carpool. What are the odds that exactly 3 out of 4 people fail to carpool?

## Recommended Posts

• 0

The odds of 3 of 4 people failing to carpool is either 0 or 1. Jay is asking the odds of a a certain probability. What are the odds that the chances of rolling a 6 on one roll with one die is 1/6? The carpool ratio, as well as the die roll ratio, is already set so it either is or it isn't 3 of 4 fail.

"Do or do not; there is no try."

##### Share on other sites
• 0

Survey results have error margins that quantify accuracy - the odds that the results are correct.

If the odds mentioned in the question depend on the survey's error margins, not given, then the question can't be answered.

So let's lay that point aside, and just think about the likelihood of the survey results themselves.

My guess would be that fewer than 25% of people car pool.

But if that were the result, the question likely would have been worded otherwise.

Based on the wording of the question I'll guess that 25% of those surveyed said they carpool,

so that the odds could be said to be 100% that exactly 75% fail to carpool.

##### Share on other sites
• 0

So if 3 out of 4 are not carpooling, who is the 4th guy riding with?

So that was the punchline. I figured that at least someone would mess up by assuming the odds are out of 4 when in reality this is unanswerable without knowing the size of the group surveyed.

##### Share on other sites
• 0
So if 3 out of 4 are not carpooling, who is the 4th guy riding with?

So that was the punchline. I figured that at least someone would mess up by assuming the odds are out of 4 when in reality this is unanswerable without knowing the size of the group surveyed.

I did think that; how could 1 person carpool? I didn't think it was a meaningful answer and did not submit it (though that hasn't stopped me before )

##### Share on other sites
• 0

I've been working so many probability problems on here over the last week that I instantly see all fractions as percentages and not sets.

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×