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Mathematics: Post your doubts here!

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yeah i know that much.. that leaves us with -a//root21 <Z < a/root21 = 0.5
what to do after that! i dont understand how ms got 0.75..
I mentioned somewhere a few minutes ago that this will lead to
2fi(a/root21)-1 = .5
fi(a/root21) = 1.5/2
fi(a/root 21) = .75
 
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View attachment 10552

how about this? I'm so confused when it comes to probability distribution T.T
Ok so the table will be like this, 5 girls and 3 boys , and a team of 4. so at minimum we can have 3 guys and 1 girl.
B- boy. G- girl
BBBG = 5C1
BBGG= 3C2*5C2
BGGG= 3C1*5C3
GGGG= 5C4
Add them up to get total possibilities. Divide each value above by this Total possibilities to get its probability. Hope this is it.
X..........1...2....3....4....
P(X)....
 
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Eight cards are selected with replacement from a standard pack of playing cards
with 12 pic cards, 20 odd cards
and 20even cards.
a) how many different sequences of cards are possible?
b) how many of the sequencees in part (a) will contain three picture cards, three odd cars and two even cards??

Part a is either 52C8 or 52P8. If each picture is different then its P.
b) 12C3 * 20C3 * 20C2 OR P as im not sure about the pictures being different.
 
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Ok so the table will be like this, 5 girls and 3 boys , and a team of 4. so at minimum we can have 3 guys and 1 girl.
B- boy. G- girl
BBBG = 5C1
BBGG= 3C2*5C2
BGGG= 3C1*5C3
GGGG= 5C4
Add them up to get total possibilities. Divide each value above by this Total possibilities to get its probability. Hope this is it.
X..........1...2....3....4....
P(X)....
oh I got it.. i took time until I realised that 3C3 is actually 1(for boy).. I appreciate ur help. thanks
 
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But where was this from? u just had to multiply what i gave with V right?
I donno .. I think Im still confused =[ but it helped that you tried.

And its from A2 mechanics (which Ive never studied, long story)... my paper is tomorrow and there's no one here who does A2 mech so......
 
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The 94% probability is the area in the MIDDLE, which means there is a "tail" on either side, of 3% probability. When you look for z value you need to count from the left side, or negative infinity. So here the probability is 0.94 + 0.03 = 0.97
View attachment 10051
how should i know when to use this method and when to simply use the probability given?
 
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