2002 q4 (a) (i) and (ii) (1 Viewer)

[Managore]

Could someone post up the answers quickly for this, if they have them? Thanks

 

[Bi0mic]

Q4

a(i)

10 x (2^9 /3^10) ... ( in unsimplified form as the question specified )

a(ii)

1 - ( 12 x (2^9 / 3^10) )

can someone please confirm these ? .. thx

 

[BillyMak]

It's binomial probability. She hits the target 2/3 times and takes 10 shots, so the binomial expansion is

((2/3) + (1/3))¹⁰

(i) P(she hits target exactly 9 times) = 10C9 (2/3)⁹(1/3)
(ii) P(she hits the target less than 9 times) = 1 - P(she hits the target 9 times or 10 times)

= 1-[10C9(2/3)⁹(1/3) + 10C10(2/3)¹⁰]

 

[Managore]

Okay thanks, I had pretty much that but wasnt sure about the x10 (aka 10C9) bit, thanks

 

[Managore]

what about 2002 question 3 (a) (ii) I have 600 as the answer, want to confirm it

 

[BillyMak]

I got 480....

 

[BillyMak]

7 people sitted at a round table, which can be done 6! ways.
2 people refuse to sit to each other. The number of ways that they can sit next to each other is 2!5! = 240 :. the number of ways that they can't sit to each other is 6! - 2!5! = 720 - 240 = 480

 

[Managore]

Yeah I did another silly mistake, 480 is right. I keep ignoring the posibility of them sitting on different sides to each other