S1 question

[crash250]

1) in how many ways can a committee of four men and four women be seated in a row if no one is seated next to a person of same sex?
2) six people r going to travel in a six seated minibus but only three of them can drive , in how many ways they can seat themselves

 

[stxjunk]

1) 5P4x5!=14400 ways
2) For driver: 3C1, rest: 5!, so, n=5!x3C1=360 ways.

 

[crash250]

for the first one i think it is 4!x4!x2=1152

and sec one can i write it like this 5P3x3!=360 ways

waiting for ur comments

 

[ahmed t]

both of your ansers are correct!

 

[mrpaudel]

yeah....u r right crash250..!!

 

[crash250]

ten people in two cars travel: a saloon and mini . if the saloon has seats for six and the mini has seats for four.in how many ways in which the party can travel.assuming order of seating does not matter and all ppl can drive?????

 

[crash250]

is it 10C4 or 10C6

 

[ahmed t]

10C4 and 10C6 are the same
due to symmetry

 

[crash250]

why we dont take them both and just add them why we have take n only one ahmed

 

[ks136]

is it 10C4 or 10C6

right

 

[ahmed t]

we must choose selections of 4 for the mini AND 6 for saloon
so we could select 4 from 10
wich will be 10C4 AND(which means times) 6 for the saloon.
so it will be 10C4 * 6C6(since we already took 4 there are 6 ppl left)
or we can pick 6 for the saloon AND then 4 for the mini
so it will be
10C6 * 4C4

remember nCn is 1
so it will be 10C6 or 10C4

 

[crash250]

hehehe..i wonderful analyzing ahmedy..got it

i will be posting some other permutation and combination questions here so that everyone can have an idea..

 

[ahmed t]

please do!

 

[histephenson007]

uhm...does statistics have any grade boundaries too???
please........... say yes

 

[ahmed t]

yes it does usually about 40-43/50 for an A

 

[histephenson007]

yes it does usually about 40-43/50 for an A

LIFESAVER~

 

[histephenson007]

Question :

A box contains 300 discs of different colours. There are 100 pink, 100 blue, 100 orange. Discs of each colour are numbered from 0 to 99. Five discs are selected at random, one at a time, with replacement.

i) find the probability that exactly 2 discs with numbers ending in a 6 are selected.

ii) find the probability that exactly 2 orange discs with numbers ending in a 6 are selected.

 

[ahmed t]

came across this in pastpapers
for i)the probability for it bieng a number ending in a six is 30/300
so we use binomial way
5C2*(0.1^2)*(0.9^3)

for part ii)
probability of orange and 6 at the end is 10/300
so it will be using binomial expansion
5C2*(1/3 ^2)*(2/3 ^3)

 

[crash250]

ahmed for part two its 1/30 not 1/3 in the binomal expression

 

[ahmed t]

oh sorry yes its 1/30
so the other one is 29/30