Probability question

[GatorWell]

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Hi, i am studying for DAT and I am having trouble figurin out these questions. If you can help me out, it will be great!

1. What is the probability of getting 6 tails outta 9 fair coin tosses?

2. Third expansion factor of (X +3)^5 ?

answer: 90X^3

Thanks!

 

[rsweeney]

1. What is the probability of getting 6 tails outta 9 fair coin tosses?

With the example above set up the problem this way:

1) (n, k)

n= total number of tosses=9
k= number of interest =6 (you want 6 tails)

SO, (9,6)

Pluge 9 and 6 into this equation (you'll love it )


n!
------- X P(favorable)^k X P(unfavorable)^(n-k)
k!(k-n)!


(!) means factorial. Forexample 3! = 3X2X1
(P) means probability
(^) means exponent---"to the"
(X) means multiplied by---its not a variable
Therefore:

9!
---------- X (1/2)^6 X (1/2)^(3) = 0.164 or ~1/6.25
6!(9-6)!

I calculated it on the computer, so I may be totally wrong, but the equation is right.


2. Third expansion factor of (X +3)^5 ?
Beats me
😛 😕

 

[critterbug]

Originally posted by GatorWell
......

2. Third expansion factor of (X +3)^5 ?

answer: 90X^3

Thanks!

WTF😕

 

[GatorWell]

Thanks~ But I already took my DAT this morning 🙂 THank you for your help tho :0

 

[critterbug]

How'd ya do?