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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

A public bus arrives at the bus stop sometime between 6:00 and 6:30.

A passenger arrives at the same bus stop some random time within this time interval. What is the probability that the passenger catches the bus within 5 minutes from the time he arrives at the stop?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Hi anna_gg;

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,000

I got

.Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Hi anonimnystefy;

Yes, that is what I am getting now also. Very good!

Although this is a continuous probability we can model it with a discrete one.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,000

*Last edited by anonimnystefy (2012-07-04 05:04:28)*

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

Excellent! Thanks!!

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Hi anna_gg;

Where does the problem come from?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

anonimnystefy wrote:

Are you sure the result is 1/72? I am getting 15/72!

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

bobbym wrote:

Hi anna_gg;

Where does the problem come from?

It was in one of my son's final exams in high school. Obviously he did it all wrong - he got 1/6

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Hi anna_gg;

That is what I got at first too. Did they give him some partial credit for getting the same answer as I did?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,000

Hi anna_gg

My answer is 11/72 and not 1/72 and it is same as bobbym's so I deduce that it is correct.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Hi anna_gg;

Anonimnystefy's answer is 11 / 72 not 1 / 72. I am pretty sure that it is the correct answer because it can be derived in 3 different ways.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

bobbym wrote:

Hi anna_gg;

Anonimnystefy's answer is 11 / 72 not 1 / 72. I am pretty sure that it is the correct answer because it can be derived in 3 different ways.

Sorry, that's what I meant, 11/72. I am just saying that:

5/6 * 1/6 + 1/6 * 5/12=15/72, isn't it?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Hi;

That equals 5 / 24.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

anna_gg wrote:

bobbym wrote:Hi anna_gg;

Anonimnystefy's answer is 11 / 72 not 1 / 72. I am pretty sure that it is the correct answer because it can be derived in 3 different ways.

Sorry, that's what I meant, 11/72. I am just saying that:

5/6 * 1/6 + 1/6 * 5/12=15/72, isn't it?

OK got it:

Anonimnystefy, it's 5/6 * 1/6 + 1/6 * 1/12 (and not 5/12)=11/72

The area of the triangle you are referring to, is (1/6 * 5/30)/2 = 1/6 * 1/12

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Hi anna_gg;

Probably just a typo.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

bobbym wrote:

Hi anna_gg;

Probably just a typo.

Obviously, no worries

BTW my son got 2/5 on this question

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Hi;

Is that good?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

NO He got 2 points out of 5 for this question... That's the partial credit you were referring to...

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Sorry to hear that. Probability problems are tough for everybody, tell him not to feel bad. Personally, I feel the problem is too strong for high school.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

bobbym wrote:

Sorry to hear that. Probability problems are tough for everybody, tell him not to feel bad. Personally, I feel the problem is too strong for high school.

Not if you are a candidate to the polytechnic

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Which one?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

bobbym wrote:

Which one?

In Greece - National Technical University of Athens. We are Greeks

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,283

Very good! You must be very proud of him. What would he like to do as his life's work?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**anna_gg****Member**- Registered: 2012-01-10
- Posts: 219

bobbym wrote:

Very good! You must be very proud of him. What would he like to do as his life's work?

He wants to become a mechanical or electrical engineer.

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