# Can some help me on this Log. word problem?

• Nov 25th 2007, 08:37 PM
Darkhrse99
Can some help me on this Log. word problem?
Determine the probablilty that x=5 people will enter in the next minute.

The formula given is p(x) 4^x e^-4/ x!

where x!= x* (x-1)*(x-2).......3*2*1

Thanks

Jason
• Nov 25th 2007, 10:17 PM
CaptainBlack
Quote:

Originally Posted by Darkhrse99
Determine the probablilty that x=5 people will enter in the next minute.

The formula given is p(x) 4^x e^-4/ x!

where x!= x* (x-1)*(x-2).......3*2*1

Thanks

Jason

And have you tried putting $\displaystyle x=5$ in:

$\displaystyle p(x) = \frac{4^x e^{-4}}{ x!}$

RonL
• Nov 26th 2007, 01:37 PM
Darkhrse99
If I put X=5 i for x I'd get

$\displaystyle p(x)=\frac{4^5 e^{-4}}{ x!}$
How would I solve it?
• Nov 26th 2007, 06:03 PM
Jhevon
Quote:

Originally Posted by Darkhrse99
If I put X=5 i for x I'd get

$\displaystyle p(x)=\frac{4^5 e^{-4}}{ x!}$
How would I solve it?

and what about the x in the denominator?
• Nov 26th 2007, 08:34 PM
CaptainBlack
Quote:

Originally Posted by Darkhrse99
If I put X=5 i for x I'd get

$\displaystyle p(x)=\frac{4^5 e^{-4}}{ x!}$
How would I solve it?

$\displaystyle p(x)=\frac{4^5 e^{-4}}{ 5!}=\frac{4^5 e^{-4}}{ 5\times4\times 3\times 2 \times 1}$

Now do you have a calculator?

RonL
• Nov 27th 2007, 07:40 AM
Darkhrse99
$\displaystyle p(x)=\frac{1024 }{120}$ = .15
• Nov 27th 2007, 07:47 AM
janvdl
Quote:

Originally Posted by Darkhrse99
$\displaystyle p(x)=\frac{1024 }{120}$ = .15

Yes i got 0,15 too.

0,1562934519 to be precise.

So that should be a chance of 15,629 % approx.

EDIT: Check your calculations. $\displaystyle 1024 \div 120$ is definitely not smaller than 1... And it's equal to 8,533 not 0,15 or even 15...
• Nov 27th 2007, 07:54 AM
janvdl
Quote:

Originally Posted by Darkhrse99
Sorry about that 1024 / 120 is 8.533.

But $\displaystyle 4^5 e^{-4} = 18,75521422$
• Nov 27th 2007, 07:55 AM
Darkhrse99
$\displaystyle p(x)=\frac{1024 e^{-4}}{ 120}$ =.1540
• Nov 27th 2007, 07:58 AM
Darkhrse99
$\displaystyle p(x)=\frac{18.4839}{ 120}$=.1540 chance of someone waling through the door.
• Nov 27th 2007, 08:02 AM
janvdl
Quote:

Originally Posted by Darkhrse99
$\displaystyle p(x)=\frac{18.4839}{ 120}$=.1540 chance of someone waling through the door.

Yes i guess our calculators work differently. That's close enough.
• Nov 27th 2007, 08:09 AM
Darkhrse99
Thanks for the help. I would have never guessed that x! means 5*4*3*2.....
• Nov 27th 2007, 08:12 AM
janvdl
Quote:

Originally Posted by Darkhrse99
Thanks for the help. I would have never guessed that x! means 5*4*3*2.....

It's the factorial of 5.

1! = 1

2! = 1 x 2

3! = 1 x 2 x 3

4! = 1 x 2 x 3 x 4

You get the idea. ;)
• Nov 27th 2007, 10:34 AM
Darkhrse99
I understand it now, but I was never aware of it before. I was never taught that in class, but I have it for homework. It's a little frustrating.
• Nov 27th 2007, 11:40 AM
bjhopper
probability
the formula for p(x) you posted must be related to some defined conditions. a p of .15 is high. it could be true in a school office given school population and average daily traffic but the p of this event for visitors coming to my house in the next minute is close to zero. what were your conditions?