Pls help...........
My problem exercise goes like this - An employee of the records office at a certain school currently has 10 forms on his desk awaiting processing, six of these are withdrawal petitions and the other four are course substitution request.
a. if he randomly select six of these forms to give to a subordinate, what is the probability that only one of the two types of forms remains on his desk?
b. suppose he has time to process only four of these forms before leaving for the day. If four are randomly selected one by one, what is the probability that each succeeding form is of a different type from its predecessor?
You have to think about what's being asked. There's no formula we can recommend for this, but a good approach is to break it up into parts.
a. P[only one of the two types remains on desk] = P[only withdrawals remain on desk] + P[only substitutions remain on desk]
To find P[only withdrawals remain on desk], think about it: to have only withdrawals remaining, you need to pick all 4 of the substitutions, and 2 of the withdrawals.
b. P[alternating for 4 forms] = P[W, S, W, S] + P[S, W, S, W]
where W=withdrawal, S=submission
We have P[W, S, W, S] = (6/10) * (4/9) * (5/8) * (3/7)
thanks joe... I am stuck on letter a. question, don't know where to start
for P(pick all 6 W's)
how many ways can you choose the 6 from the 10 total
when picking 6 how many ways can you pick all 6 W's
(remember order doesn't matter here)
----------------
for P(pick all 4 S's)
again how many ways can you choose the 6 from the 10 total
how many ways to pick the 4 S's and how many ways to pick 2 W's out of the 6
can you show me the formula please so I can start..thanks
I'm still confused. What I only know is the probability of getting 6 withdrawal forms is 0.00476... can you expound your computation please.
i got the same answer 0.00476 for 4C4*6C2/10C6. don't know how you got 15/210
so the probability that only one of the two types of froms remain on the desk is 0.0762. is that right?
regarding the second question, quoting your answer below, is the final answer 0.1429?
b. P[alternating for 4 forms] = P[W, S, W, S] + P[S, W, S, W]
where W=withdrawal, S=submission
We have P[W, S, W, S] = (6/10) * (4/9) * (5/8) * (3/7)
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