Questions (1 Viewer)

[allGenreGamer]

Some questions that I need to figure out before the test:

1. Eight people are divided into two groups. What's the probability that there will be 4 in each group?

2. The letters of the word "promise" are arranged in a row. What's the probability that there's 3 letters between p an r?

Thanks.

 

[George W. Bush]

First one is 8C4/ 8C1 + 8C2 + 8C3 + 8C4, assuming there has to be one person in each group.

 

[~*HSC 4 life*~]

i'm soooooo bad at probability...i don't get your answer G. Bush? can you explain it?

when i read the Q i just thought to myself...well ok the possible ways the could make 2 gourps out of 8 people...

1/ we can have one person in the 1st group and 7 ppl in the 2nd

OR

2/ 2 ppl in the 1st group, 6 ppl in the 2nd

3/ 3 ppl in the 1st group, 5 pplin the second

4/ 4 ppl in the first group, 4 ppl in the second

(and if i go on...5 ppl in the 1st group, 3 ppl in the second, it is the same as choice 3/ above, and so on and so forth)

so i just thought here, you got 4 possible groups u can make, but the prob of gettign 4 in each group is 1/4

bah!

 

[George W. Bush]

OK for 4 people in a group thats 8C4 (the other group obv has 8-4=4)

Total arrangements = 1 person in a group 8C1 + 2 persons in a group 8C2 + 3 persons...8C3 + 8C4

we dont need to worry about 5-7 because say, having five in 1 group is the same as having three in the other..