again probability Q

charly2012

I suspect you've calculated P(low then medium then high), but you've left out events like (low then high then medium), which also should be counted.

Reply 2

charly2012

OP

1

errrm so how many time do i have to do this ? i thought you do it for 3 days

Reply 3

Caribbeantwist

12

Yes each probability equals for 3 days
So like the previous poster said it could be different combination like
Low, medium, high
Or
High, medium, low
Or
Medium, low, high
Or
Medium, high, low

Etc etc.

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Reply 4

Secret.

14

Original post by charly2012

errrm so how many time do i have to do this ? i thought you do it for 3 days

The possibilities within the 3 days are
LMH
LHM
HML
HLM
MLH
MHL

Reply 5

charly2012

OP

1

Original post by Secret.

The possibilities within the 3 days are
LMH
LHM
HML
HLM
MLH
MHL

say we take only one day : would it be (LMH) (LHM) (HML) which means any of them start 1st following by others ?

Reply 6

Secret.

14

Original post by charly2012

say we take only one day : would it be (LMH) (LHM) (HML) which means any of them start 1st following by others ?

On one day it can only be L or H or M, not 3 as the combination of 3 is for 3 days, each one on 1 day if that makes sense

Reply 7

charly2012

OP

1

Yes , but how am i mean to know in question like these , how many time do i need them for the given day .

i mean as you said you need combination of all in various order . but how am i meant to know how many combination do i need please explain . thanks

Reply 8

Caribbeantwist

12

Original post by charly2012

Yes , but how am i mean to know in question like these , how many time do i need them for the given day .

i mean as you said you need combination of all in various order . but how am i meant to know how many combination do i need please explain . thanks

Basically you have to think about it.
You need to calculate the probability that in a period of 3 days, one day will be high, one medium and one low.
If you calculate high and medium and low, that is only going to give the probability of that combination. As the question does not specify a combination, you have to calculate the probability that covers all possible outcomes where in a 3 day period one day is high, one low and one medium. Do you understand now??

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Reply 9

charly2012

OP

1

hold on sorry , say if they ask you to find it for 10 days , in this case you have to keep do as many combination as you can ? wouldnt that be just a waste of time ? IS any other way of answering this kind of question ?

to be really certain it confuses me when it comes to adding combination of them as you wouldn't know how many you need if they asked yo ufor 10 days or more say :s-smilie:

Reply 10

Caribbeantwist

12

Original post by charly2012

hold on sorry , say if they ask you to find it for 10 days , in this case you have to keep do as many combination as you can ? wouldnt that be just a waste of time ? IS any other way of answering this kind of question ?

to be really certain it confuses me when it comes to adding combination of them as you wouldn't know how many you need if they asked yo ufor 10 days or more say :s-smilie:

They would never ask you for 10 days because that would be 120 combinations (10 nCr 3)

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Reply 11

charly2012

OP

1

so if you need 120 combinatin for 10 days , how can i find out the combination for 3 or 4 days which they may ask ?

Because if you know the amount of combination you need , then you can raise you answer to the power of the combination right ?

thanks in advance

Reply 12

Caribbeantwist

12

Original post by charly2012

so if you need 120 combinatin for 10 days , how can i find out the combination for 3 or 4 days which they may ask ?

Because if you know the amount of combination you need , then you can raise you answer to the power of the combination right ?

thanks in advance

Hang on my combination was wrong

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Reply 13

BabyMaths

Original post by charly2012

so if you need 120 combinatin for 10 days , how can i find out the combination for 3 or 4 days which they may ask ?

Because if you know the amount of combination you need , then you can raise you answer to the power of the combination right ?

thanks in advance

What exactly are you after here? How many ways 4 days can include at least one L, at least one M and at least one H?

Reply 14

Caribbeantwist

12

They would never ask for the number of combinations, it's literally just a case of thinking it out. If you want to check you've covered every possibility then if you put the number of options (in this case 3) to the number of choices (however many days you need) which will give you a number which you can then use to check that you have exhausted your options

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Reply 15

charly2012

OP

1

Original post by BabyMaths

What exactly are you after here? How many ways 4 days can include at least one L, at least one M and at least one H?

Q/ probability of low one day , medium one day and hight another day .

the problem is i cnt figure out how many combination do i need .

The mark scheme says (L x M x H ) ^6

but why to the power of 6 ?

OR HOW DO I KNOW IT is to the power of which number ?

Reply 16

BabyMaths

Original post by charly2012

Q/ probability of low one day , medium one day and hight another day .

the problem is i cnt figure out how many combination do i need .

The mark scheme says (L x M x H ) ^6

but why to the power of 6 ?

OR HOW DO I KNOW IT is to the power of which number ?

Post your question exactly as it was given to you.

Reply 17

lelikins

I would have worked out it was 6 by doing 3nPr3 on my calculator - you are looking at the number of ways you can choose three letters out of a total of three when order does matter.