# S2 practice question help

Watch
Announcements
This discussion is closed.
#1

A six-sided die is biased. When the die is thrown the number 5 is twice as likely to appear as any other number. All other faces are equally likely to appear. The die is thrown repeatedly.

Find the probability that

i) the first 5 will occur on the sixth throw,

ii) in the first eight throws there will be exactly three 5's

Thanks
0
15 years ago
#2
where did you get this question? this best not be in todays paper
0
15 years ago
#3
It is off last years...

p(x=5)= 2/7
p(x not = 5)= 5/7

i)
p(x on 6th throw) = (2/7)*(5/7)^5

ii)
p(3 5s in 8 throws) = 8C3*(2/7)^3*(5/7)^5

This is how I done it anyways
0
X
new posts
Back
to top

view all
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

Yes (61)
51.69%
Yes, but I want to swap them (10)
8.47%
No, but I know who I want to choose (14)
11.86%
No, I still don't know who I want to choose (30)
25.42%
I have decided I don't want to go to uni anymore and will not be choosing (3)
2.54%