Page 1 of 1 [ 1 post ]
 Print view Previous topic | Next topic
Author Message
 Post subject: Combinatoris & Probability Book, Drill page 52Posted: Fri Jan 06, 2012 12:03 pm

Joined: Thu Feb 12, 2009 6:32 pm
Posts: 497
#1.
There are 8 possible outcomes when we flip a coin three times. (2*2*2 for 2 outcome possibilities on each flip)
We want 2 heads in a row -
So we can have one of three scenarios that work:
1. no tails at all (HHH)
2. Tails in first flip (THH)
3. Tails in third flip (HHT)

So our answer is 3/8.

#2.
This one is like the last one except that we add one more scenario:
4. Tails as second flip (HTH)
So we have 4 outcomes out of 8 total that fit our criteria, or 4/8 as answer.

#3.

We want two threes in a row (probability of each is 1/6)
followed by a different number (probability of this is 5/6)
So we have:
1/6 * 1/6 * 5/6 or 5/216.

The other way to look at this one is this:
There are 216 possible outcomes (6 sides possible each roll, and three rolls, so 6*6*6 = 216.)
The outcomes we like are:
331
332
334
335
336
There are 5 of these, so 5/216 is our answer.

#4.
There are 6*6*6 = 216 possible outcomes.

There are 3 general ways to exactly 2 6's:
66x
6x6
x66

where x = one of the other numbers: 1,2,3,4, or 5
there are 5 ways to get each of the above for example: 661, 662, 663, 664, 665
there are 5 * 3 = 15 ways to get exactly 2 sixes

so, the probability is 15/216

-- Veritas Help

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 1 post ]

 All times are UTC - 8 hours [ DST ]

#### Who is online

Users browsing this forum: No registered users and 1 guest

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

 Search for: