
May 27th, 2005, 01:01 PM
#1
Anyone good at maths? (probability)
Stuck with some basic maths probabilty.....
Heres my question guys:
[b]a component is made in 3 stages. the first stage involves building from one of four machines A,B,C and D all with equal probabilites. Second stage is trimmed using one machine either E,F or G, and finally polished using either machine H or J and it is twice as likely to be the former as H works faster[b]
Determine the porbabilty of:
1. a component is polished on machine H
is it 2:1?
2. it is trimmed on either machine F or G
2/3 or 66%
[b]3. a component is formed on either machine A or B, trimmed on F and polished on H]/b]
i have no idea
4. it is formed on machine A and polished on J
??
5. formed on machine B and polished on machine H
6. formed on machine A and trimmed on F
A = 1/4 or 0.25, F = 1/3 or 0.3
0.25 x 0.3 = 0.075
0.25 + 0.3  0.075 = 0.475 or 47.5%
is that right?
any help on this guys would be a big help, show working out too?

May 27th, 2005, 04:50 PM
#2
i would probably fail whatever class those questions are from

May 27th, 2005, 06:58 PM
#3
now its late, I am drunk and have no paper, still, I think its like this:
1. is 2/3
2. is 2/3
3. is 1/9
4. is 1/12
5. is 1/6
6. is 1/12
Basically you set probabilty to each event on each stage separately.
You have 3 stages and you always multiply in between. (if the probability of getting through certain stage is 1/4 and through another stage is 1/3, then MP it will give you 1/12)
However when its "OR" on certain stage, you add the probabilities for all events "OR" includes.
And when certain stage is left out the probabilty is of course 1, since it has to go via that stage anyway.
hope that makes some sense
Last edited by F_A_L_C_O_N; May 27th, 2005 at 07:06 PM.

May 27th, 2005, 08:00 PM
#4
Re: Anyone good at maths? (probability)
Originally posted by adam1v
A = 1/4 or 0.25, F = 1/3 or 0.3
0.25 x 0.3 = 0.075
0.25 + 0.3  0.075 = 0.475 or 47.5%
is that right?
any help on this guys would be a big help, show working out too?
no.
1/3=0.333333333
also you multiply for "and" and add for "or", here you seem to do both. Why ?
So as Falcon suggested, 1/4 x 1/3 = 1/12 = 0.083333 = 8.333%
Looking intelligent takes more than looking coool.

May 28th, 2005, 04:29 AM
#5
Originally posted by F_A_L_C_O_N
now its late, I am drunk and have no paper, still, I think its like this:
1. is 2/3
2. is 2/3
3. is 1/9
4. is 1/12
5. is 1/6
6. is 1/12
Basically you set probabilty to each event on each stage separately.
You have 3 stages and you always multiply in between. (if the probability of getting through certain stage is 1/4 and through another stage is 1/3, then MP it will give you 1/12)
However when its "OR" on certain stage, you add the probabilities for all events "OR" includes.
And when certain stage is left out the probabilty is of course 1, since it has to go via that stage anyway.
hope that makes some sense
Thanks falcon, i have drawn a tree chart now and see how you have done it.
makes great sense now, thanks mate.
Adam

May 28th, 2005, 03:17 PM
#6
LOL Are you coming on here to get homework help xD
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May 29th, 2005, 03:44 AM
#7
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