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?

i would probably fail whatever class those questions are from;)

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 :p

Quote:

---

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%

Quote:

---

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 :p

---

Thanks falcon, i have drawn a tree chart now and see how you have done it.
makes great sense now, thanks mate.

Adam

LOL Are you coming on here to get homework help :D :p xD

Quote:

---

Originally posted by ThePerson98
LOL Are you coming on here to get homework help :D :p xD

---

Yep, but now i understand better, and finish off the other 20 questions :o