VCE Methods Question Thread!

[knightrider]

I did help you with that question - I'd suggest finding the z-score. Also, remember that a normal distribution is symmetrical about the mean - consider drawing the distribution and shade under the curve what each probability is referencing.

Thanks EulerFan101 

but when you find the z-score you get

(22-16)/4=6/4=3/2

The answer says a=10 how ?

[keltingmeith]

Thanks EulerFan101 

but when you find the z-score you get

(22-16)/4=6/4=3/2

The answer says a=10 how ?

The z-score doesn't give you the answer. But, combining the z-score with the fact that the normal distribution is symmetrical about the mean (which is x=0 for the standard normal), puts you on the right path. I suggest drawing in a normal distribution with Pr(X>22) sketched in, and Pr(X<a) sketched in, and see if that stimulates any ideas.

[cosine]

Few questions I could not do from a practice exam, I need help with it and listed all options so that anyone who wants to try them also can.

Question 1:
The height of a tide, h meters, at the entrance to a port is given by where t is the number of hours after midnight and a is a positive integer. The number of times the height is 10m within the first day is?

A. 3
B. 6
C. 6/a
D. 3a
E. 6a

For this one, I just don't know what to do... The value of  a can drastically change the amount of times it reaches 10 m.

Question 2:
Two dice are rolled. The probability distribution for X, the difference between the numbers on the dice, is given by:

x:              0       1          2        3     4     5
Pr(X=x)  6/36  10/36   8/36     a      b   2/36

The probability that X is less than 2 given that X is less than 4 is:

A. 8/18
B. 8/15
C. 12/17
D. 17/18
E. 2/3

For this one, I cannot work out a or b because I can only formulate one equation. So I used and I know that for X to be less than 2, it is ALWAYS less than 4, so I know have: . But now I have no idea how to work it out.

Many thanks.

[StupidProdigy]

Few questions I could not do from a practice exam, I need help with it and listed all options so that anyone who wants to try them also can.

Question 1:
The height of a tide, h meters, at the entrance to a port is given by where t is the number of hours after midnight and a is a positive integer. The number of times the height is 10m within the first day is?

A. 3
B. 6
C. 6/a
D. 3a
E. 6a

For this one, I just don't know what to do... The value of  a can drastically change the amount of times it reaches 10 m.

Question 2:
Two dice are rolled. The probability distribution for X, the difference between the numbers on the dice, is given by:

x:              0       1          2        3     4     5
Pr(X=x)  6/36  10/36   8/36     a      b   2/36

The probability that X is less than 2 given that X is less than 4 is:

A. 8/18
B. 8/15
C. 12/17
D. 17/18
E. 2/3

For this one, I cannot work out a or b because I can only formulate one equation. So I used and I know that for X to be less than 2, it is ALWAYS less than 4, so I know have: . But now I have no idea how to work it out.

Many thanks.

2nd question. Pr(X=a) is 6/36. This is all you need as you already know. Now you can just plug it into the working you did at the end. It's 6/36 because the outcomes we can have where the difference between the dice is 5 are: rolling a six and rolling a 1 (diff=6-1=5) which can occur twice, 2 lots of 5-2, two lots of 4-1 giving us six outcomes out of 36 where the difference can equal to 5. Does this make sense? I think it has the two unknowns to trick people into using simultaneous equations even though there isn't enough info

[cosine]

2nd question. Pr(X=a) is 6/36. This is all you need as you already know. Now you can just plug it into the working you did at the end. It's 6/36 because the outcomes we can have where the difference between the dice is 5 are: rolling a six and rolling a 1 (diff=6-1=5) which can occur twice, 2 lots of 5-2, two lots of 4-1 giving us six outcomes out of 36 where the difference can equal to 5. Does this make sense? I think it has the two unknowns to trick people into using simultaneous equations even though there isn't enough info

No, not really... So what's the answer?

[StupidProdigy]

No, not really... So what's the answer?

Okay new approach. Grab two dies. Shuffle the upwards facing numbers around on them until there is a difference of 5 between the two upper presented numbers. How many ways can you make the difference five?
The answer is B yes?  ((16/36)/(6/36+10/36+8/36+6/36))=8/15

[cosine]

Okay new approach. Grab two dies. Shuffle the upwards facing numbers around on them until there is a difference of 5 between the two upper presented numbers. How many ways can you make the difference five?
The answer is B yes?  ((16/36)/(6/36+10/36+8/36+6/36))=8/15

Can you show me the systematic way of doing this? I included my working out and the formulas because I needed someone to show me the way to do it that involved the formulas. (I am not really good with logically thinking about the probabilities)

[cosine]

Attached question:

In exam 1, are we required, for a 1 mark question, to convert those decimals into the fraction? If so, how do we know that it's equal to 3/8? Cheers.

[keltingmeith]

Attached question:

In exam 1, are we required, for a 1 mark question, to convert those decimals into the fraction? If so, how do we know that it's equal to 3/8? Cheers.

Multiply numerator and denominator by 100.
Simplify fraction.

[cosine]

Multiply numerator and denominator by 100.
Simplify fraction.

Cheers Eulerfan, but would leaving the answer as the decimal fraction suffice for a 1 mark question? Or is this too vague of a question as it depends on the examiner?

Also, should I/someone make a thread about specifics about exams and not methods-direct questions? Or are we allowed to ask here, for example, I mistakenly graphed function for all x real numbers, but the question wanted only for x>2. However, the shape and require x-intercepts were all valid and included, would marks be lost or was this just a case of wasting time? (Can you answer this please, and also about making a new thread or not?)

Many thanks

[keltingmeith]

Cheers Eulerfan, but would leaving the answer as the decimal fraction suffice for a 1 mark question? Or is this too vague of a question as it depends on the examiner?

Also, should I/someone make a thread about specifics about exams and not methods-direct questions? Or are we allowed to ask here, for example, I mistakenly graphed function for all x real numbers, but the question wanted only for x>2. However, the shape and require x-intercepts were all valid and included, would marks be lost or was this just a case of wasting time? (Can you answer this please, and also about making a new thread or not?)

Many thanks

Sorry - when I wrote it, I thought I said this, but I clearly forgot and could only think about food. >.<

Regardless of how many marks a question is worth, you should simplify fractions when able. And never, ever, leave a fraction with decimals in it. ALWAYS convert these to integers. You can write decimals instead of fractions, but never both.

You will lose a mark if you use the wrong domain. This probably counts as your shape mark, but I'm not sure about that. I know you will lose it, though, because it happened in specialist in 2013 (check the examiner's report!)

You can post exam specific stuff here for now. On the lead up to the exam, I'll post an exam-technique specific topic for questions like that. It's a bit early atm.

[Floatzel98]

Are we really ever expected to graph binomial probability distribution by hand or on CAS. What kind of question could that appear in for example. My textbook only has instructions for TI-Nspire while I have the Class pad 330. For example I have the question:

Plot the probability distribution function



for n = 8 and p = 0.25

Am I expected to do this by hand or CAS, and how do I do it using either method?

[StupidProdigy]

Alright going back to primary school math...when I am asked to give 0.744748 correct to two decimal places, why is it 0.74 instead of 0.75? I thought the second 7 would round the 4 before it to a 5 and that this 5 would round the 4 before it to a 5? Sorry for such a basic question

[keltingmeith]

Alright going back to primary school math...when I am asked to give 0.744748 correct to two decimal places, why is it 0.74 instead of 0.75? I thought the second 7 would round the 4 before it to a 5 and that this 5 would round the 4 before it to a 5? Sorry for such a basic question

Nah, you only look at the number directly before the point you want to round at. Ie, you look at 0.744, then round. Not 0.7447.

[StupidProdigy]

Nah, you only look at the number directly before the point you want to round at. Ie, you look at 0.744, then round. Not 0.7447.

Ohhhhh! Thanks euler! +1