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

1. ## 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

2. 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

3. 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?

4. 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?

5. 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

6. $\displaystyle p(x)=\frac{1024 }{120}$ = .15

7. 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...

8. Originally Posted by Darkhrse99
Sorry about that 1024 / 120 is 8.533.
But $\displaystyle 4^5 e^{-4} = 18,75521422$

9. $\displaystyle p(x)=\frac{1024 e^{-4}}{ 120}$ =.1540

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

11. 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.

12. Thanks for the help. I would have never guessed that x! means 5*4*3*2.....

13. 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.

14. 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.

15. ## 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?