document.write( "Question 202488: Can someone PLEASE help me with these? Thank You. :)\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "1) A person is wearing a bracelet with 11 settings around the bracelet. How many different ways can 11 birthstones be arranged around the bracelet? Leave the answer in factorial form.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "2) How many subsets of four elements each exist in a set of seven elements?
\n" ); document.write( " \r
\n" ); document.write( "\n" ); document.write( "3) How many different groups of 35 cars can be formed from 40 cars?
\n" ); document.write( " \r
\n" ); document.write( "\n" ); document.write( "4) How many different ways can an executive committee of nine people sit at a round table?\r
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "5) What is the probability of not drawing a green marble from a jar containing 7 red, 4 green, 3 white, and 9 blue marbles?\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "6) A compound experiment consists of drawing at random twice without replacing from a jar with 3 red, 3 white, and 2 black marbles. What is the probability of getting first a red and then a black marble?\r
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "Thanks again,
\n" ); document.write( "~Sarah
\n" ); document.write( "

Algebra.Com's Answer #152724 by Theo(13342)\"\" \"About 
You can put this solution on YOUR website!
permutations are an ordered set. each set can contain the same elements as another set only in a different order.
\n" ); document.write( "the formula for permutations is:
\n" ); document.write( "\"n%21%2F%28n-x%29%21\"
\n" ); document.write( "-----
\n" ); document.write( "combinations are an unordered set. each set cannot contain the same elements as another set regardless of the order.
\n" ); document.write( "the formula for combinations is:
\n" ); document.write( "\"n%21%2F%28%28n-x%29%21%2Ax%21%29\"
\n" ); document.write( "-----
\n" ); document.write( "a simple example:
\n" ); document.write( "letters abc.
\n" ); document.write( "sets of 2 letters
\n" ); document.write( "permutations would be: ab, ba, ac, ca, bc, cb.
\n" ); document.write( "formula for permutations would be \"3%21%2F1%21\" = 6
\n" ); document.write( "note that 1! was the result of (3-2)! which = 1!.
\n" ); document.write( "combinations would be: ab, ac, bc
\n" ); document.write( "formula for combinations would be \"3%21%2F%281%21%2A2%21%29\" = 3
\n" ); document.write( "-----
\n" ); document.write( "your problems:
\n" ); document.write( "-----
\n" ); document.write( "1) A person is wearing a bracelet with 11 settings around the bracelet. How many different ways can 11 birthstones be arranged around the bracelet? Leave the answer in factorial form.
\n" ); document.write( "we're looking for permutations here.
\n" ); document.write( "the formula should be how many permutations of 11 can you get out of a set of 11.
\n" ); document.write( "the formula should be:
\n" ); document.write( "\"n%21%2F%28n-x%29%21\"
\n" ); document.write( "where:
\n" ); document.write( "n = 11 = set you are drawing from.
\n" ); document.write( "x = 11 = set you want to create.
\n" ); document.write( "\"11%21%2F%2811-11%29%21\" = \"11%21%2F0%21\" = \"11%21%2F1\" = \"11%21\".
\n" ); document.write( "please note that \"0%21\" = 1.
\n" ); document.write( "this may be counter-intuitive but it is correct. if you want to see a decent explanation, go to this website and look at the best answer to the question.
\n" ); document.write( "-----
\n" ); document.write( "http://answers.yahoo.com/question/index;_ylt=AsdGQIzGmbF_exSCD_gWWxYjzKIX;_ylv=3?qid=20060811004831AAT49h4
\n" ); document.write( "-----
\n" ); document.write( "anyway, back to your problem.
\n" ); document.write( "\"11%21\" = 11*10*9*8*7*6*5*4*3*2*1 = 39,916,800 possible ways the birthstones can be arranged on the necklace.
\n" ); document.write( "-----
\n" ); document.write( "if it was 2 beads they could be arranged \"2%21\" ways = 2*1 = 2 ways
\n" ); document.write( "if it was 3 beads they could be arranged \"3%21\" ways = 3*2*1 = 6 ways
\n" ); document.write( "if it was 4 beads they could be arranged \"4%21\" ways = 4*3*2*1 = 24 ways
\n" ); document.write( "you can see as the number of beads gets larger, the possible permutations (these are permutations because they contain the same beads only in a different order) becomes much larger.
\n" ); document.write( "-----
\n" ); document.write( "2) How many subsets of four elements each exist in a set of seven elements?
\n" ); document.write( "looks like they want combinations here since order is not important.
\n" ); document.write( "n = 7
\n" ); document.write( "x = 4
\n" ); document.write( "formula for number of combinations is \"n%21%2F%28%28n-x%29%21%2Ax%21%29\"
\n" ); document.write( "this winds up being \"7%21%2F%28%287-4%29%21%2A%284%21%29%29\"
\n" ); document.write( "which becomes:
\n" ); document.write( "\"7%21%2F%283%21%2A4%21%29\"
\n" ); document.write( "which becomes:
\n" ); document.write( "7*6*5*4*3*2*1/1*2*3*1*2*3*4
\n" ); document.write( "which becomes:
\n" ); document.write( "35
\n" ); document.write( "-----
\n" ); document.write( "The possible number of subsets = 35.
\n" ); document.write( "Each subset will not contain the same elements as any other subset.
\n" ); document.write( "Order is not important.
\n" ); document.write( "-----
\n" ); document.write( "3) How many different groups of 35 cars can be formed from 40 cars?
\n" ); document.write( "this looks like combinations again, since different groups would not contain the same cars in each group in a different order.
\n" ); document.write( "formula would be \"%2840%29%21%2F%28%2840-35%29%21%2A%2835%29%21%29\"
\n" ); document.write( "this becomes:
\n" ); document.write( "\"%2840%2A39%2A38%2A37%2A36%2A35%21%29%2F%2835%21%2A5%2A4%2A3%2A2%2A1%29\" which equals 658008
\n" ); document.write( "-----
\n" ); document.write( "4) How many different ways can an executive committee of nine people sit at a round table?
\n" ); document.write( "This should be permutations again.
\n" ); document.write( "It is similar to the beads question but only this time we have 9 executives instead of 11 beads.
\n" ); document.write( "Your answer should be 9! = 9*8*7*6*5*4*3*2*1 = 362,880.
\n" ); document.write( "-----
\n" ); document.write( "5) What is the probability of not drawing a green marble from a jar containing 7 red, 4 green, 3 white, and 9 blue marbles?
\n" ); document.write( "there are 4 green marbles in the set.
\n" ); document.write( "the probability of not drawing a green marble should be 1 - the probably of drawing a green marble.
\n" ); document.write( "the total marbles in the set are 7+4+3+9 = 23.
\n" ); document.write( "since there are 4 marbles in the set, the probability of drawing a green marble is 4/23.
\n" ); document.write( "therefore, the probability of not drawing a green marble should be 1 - 4/23 = 19/23.
\n" ); document.write( "another way of looking at it is:
\n" ); document.write( "the probability of not drawing a green marble is the probability of drawing any marble that is not green.
\n" ); document.write( "out of the 23 marbles, 19 of them are not green (7 red + 3 white + 9 blue), so the probability of drawing a marble that is not green is 19/23.
\n" ); document.write( "-----
\n" ); document.write( "6) A compound experiment consists of drawing at random twice without replacing from a jar with 3 red, 3 white, and 2 black marbles. What is the probability of getting first a red and then a black marble?
\n" ); document.write( "you start off with 3 red 3 white 2 black marlbes for a total of 8 marbles.
\n" ); document.write( "on your first draw, the probability of drawing a red marble is 3/8.
\n" ); document.write( "assuming you got the red marble you were looking for, then the probability of getting a black marble on the second draw is 2/7. the reason for this is that you got the red marble on the first draw and didn't return it into the pot so what was left was 2 red 3 white 2 black marbles.
\n" ); document.write( "----
\n" ); document.write( "now, the probability of event A happening and then event B happening is the p(A) * p(B) which means that the probability of first getting a red and then getting a black would be 3/8 * 2/7 = 6/56.
\n" ); document.write( "-----
\n" ); document.write( "you can look at that as follows: 3/8 of the time you get a red. within that 3/8 of the time, 2/7 of the time you get a black on the second draw.
\n" ); document.write( "getting them both can only happen 3/8 * 2/7 of the time.
\n" ); document.write( "try smaller number again to see what's happening.
\n" ); document.write( "you have a pot with 3 letters in it.
\n" ); document.write( "a,b,c
\n" ); document.write( "what is the probability of getting an (a) and then a (b)?
\n" ); document.write( "you will get the (a) 1/3 of the time.
\n" ); document.write( "once you get the (a), you will get the (b) 1/2 of the time, assuming you didn't return the (a) into the pile.
\n" ); document.write( "the possible combinations in order of how they were drawn is as follows:
\n" ); document.write( "ab
\n" ); document.write( "ac
\n" ); document.write( "ba
\n" ); document.write( "bc
\n" ); document.write( "ca
\n" ); document.write( "cb
\n" ); document.write( "the only successful draw would be ab which represents 1/6 of the total possible combinations.
\n" ); document.write( "1/3 * 1/2 = 1/6 so the formula of p(a) * p(b) is good and the answer for this example is 1/6.
\n" ); document.write( "It is not, however, the answer to the last question. It is only the answer to the example I just used.
\n" ); document.write( "the answer to your last question is 6/56 as I indicated above.
\n" ); document.write( "
\n" );