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#1 2012-07-03 09:11:22

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Bus stop

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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#2 2012-07-03 11:35:25

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

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#3 2012-07-03 11:43:21

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

Re: Bus stop

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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#4 2012-07-03 11:53:48

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#5 2012-07-03 12:41:01

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

Re: Bus stop

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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#6 2012-07-03 22:02:45

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

Excellent! Thanks!!

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#7 2012-07-03 22:03:37

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#8 2012-07-03 22:47:28

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

anonimnystefy wrote:

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

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#9 2012-07-03 22:50:43

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

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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#10 2012-07-04 00:17:29

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#11 2012-07-04 00:46:41

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

Re: Bus stop

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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#12 2012-07-04 01:02:25

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#13 2012-07-04 03:41:33

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

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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#14 2012-07-04 03:45:06

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#15 2012-07-04 03:57:15

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

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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#16 2012-07-04 04:09:36

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#17 2012-07-04 04:16:46

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

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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#18 2012-07-04 04:20:02

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#19 2012-07-04 04:31:23

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

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

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#20 2012-07-04 04:35:03

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#21 2012-07-04 05:32:57

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

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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#22 2012-07-04 05:35:00

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#23 2012-07-04 06:05:43

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

bobbym wrote:

Which one?

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

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#24 2012-07-04 06:09:19

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,188

Re: Bus stop

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.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#25 2012-07-04 06:26:59

anna_gg
Member
Registered: 2012-01-10
Posts: 232

Re: Bus stop

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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