Mathematics Question Thread

[Sine]

I was wondering how to do this question.
So far I gave this for part a
E(X) = 3(12) = 36

(c) Y = 2X + 5

E(X) = 12
So
E(Y) = E(2X+5) = 2E(X) + 5 = 2 * 12 + 5 = 29

Sd(X) = 3
So
Sd(Y)  = Sd(2x+5) = 2 * Sd(X) = 2 * 3  = 6

In general terms
E(aX+b) = aE(X) + b 
Sd(aX+b) = |a|Sd(X)
and for completeness
Var(aX+b) = a²Var(X)

Hopefully you can do the other questions now

[Adammurad]

An examination consists of six multiple-choice questions. Each question has four
possible answers. At least three correct answers are required to pass the examination.
Suppose that a student guesses the answer to each question.
a What is the probability the student guesses every question correctly?
b What is the probability the student will pass the examination?
Would anyone help and show the working out and solution thanks

[RuiAce]

An examination consists of six multiple-choice questions. Each question has four
possible answers. At least three correct answers are required to pass the examination.
Suppose that a student guesses the answer to each question.
a What is the probability the student guesses every question correctly?
b What is the probability the student will pass the examination?
Would anyone help and show the working out and solution thanks

The second one is a binomial-probability, which is 3U. What is the source of this question?

[Adammurad]

Cambridge Senior maths ex14a unit 3/4

[RuiAce]

Cambridge Senior maths ex14a unit 3/4

By any chance, are you after the VCE section of the forum?

[Adammurad]

sorry for that but just wondering would be able to give me the working out and solution to the question part b)

[RuiAce]

[anotherworld2b]

I am not sure how to find he standard deviation for q12. I am not quite sure what to do for q13

[RuiAce]

I am not sure how to find he standard deviation for q12. I am not quite sure what to do for q13

The standard deviation is just the square root of the variance. Once you have Var(Y), you should only be taking the square root of it to find Stddev(Y).
Note that the properties of the standard deviation are NOT similar to those of the expected value. The standard deviation is the square root of the variance and nothing else.

Hint for 13: If X is the random variable measuring the length in centimetres, then Y = 0.01X is the random variable measuring it in metres.

[12070]

Hey just wondering if I can post Uni questions as my brother needs help with engineering and if not, where should I post them? This is the question:

[RuiAce]

Hey just wondering if I can post Uni questions as my brother needs help with engineering and if so, where should I post them? This is the question:

Can you please post this not in the HSC section but down here?

[caitlinlddouglas]

Hey I was wondering why the answeR is x>0 and not all real x, x>3/2?
Find the domain of the graph for y=log|2x-3|
Thanks!

Hi I was wondering if someone could also help me with this question?
Find the equation of the line passing through the lint of intersection of 2x-3y-5=0 and x+2y=7 and the point (2,4). The solution says you need to put them together with a k in front of the second line but I don't get why? Thanks heaps

Mod edit: Posts merged. At times like this, please resort to the modify function at the top right corner of a post to refrain from double posting.

[RuiAce]

Hey I was wondering why the answeR is x>0 and not all real x, x>3/2?
Find the domain of the graph for y=log|2x-3|
Thanks!

For the other question, have you been taught the k-method in class yet?

[caitlinlddouglas]

For the other question, have you been taught the k-method in class yet?

Thanks heaps!
No I haven't been taught that but would you mind explaining it please?

[RuiAce]

To be honest, in the HSC that's either a method you just accept and take for granted, or don't use altogether. I didn't understand it until first year uni.

If you don't use it, the alternate approach is this, which is for granted:
1. Use simultaneous equations to find the point of intersection of the lines (call the point of intersection, say, P)
2. Find the gradient of the line between P and the other point, in your case being (2,4)
3. Use the point-gradient formula to find the equation of your required line.