VCE Methods Question Thread!

[pinklemonade]

Can someone please help me with question 1b?
Have no idea how to do this!

[odeaa]

Can someone please help me with question 1b?
Have no idea how to do this!

Use the invnorm function on your cas (if youre using ti-snpire its menu-5-5-3)
so invnorm(0.95,100,15) (area, mean, sd)
=124.37

Now for a question of my own, just saw J used in a general solution for an insight exam. Is this the same as Z? Can't find anything on wikipedia and dont have the textbook. Cheers

[knightrider]

How come when solving for x.

I can  cancel out the  by multiplying both sides by it ?

  Why can i do this?

[cosine]

How come when solving for x.

I can  cancel out the  by multiplying both sides by it ?

  Why can i do this?

Because you're trying to solve for x, and the only way to isolate the term 'x' is by getting rid of everything in it's way, and so multiplying both sides by the denominator allows you to solve for x by transposing 2x^2-8x. Think of it as transposing, try to solve for x another way besides this way (without calc), you will take a while xD

[2jzgte]

Can someone please explain how you would go about solving this?

[knightrider]

Because you're trying to solve for x, and the only way to isolate the term 'x' is by getting rid of everything in it's way, and so multiplying both sides by the denominator allows you to solve for x by transposing 2x^2-8x. Think of it as transposing, try to solve for x another way besides this way (without calc), you will take a while xD

Thanks cosine 

[odeaa]

Can someone please explain how you would go about solving this?

a) The transformed mean, , is equal to (because we know the original mean = 27.2)

We know that , so

Solving for gives us

Now, using the information we were given,

When you see 0.025 (or 0.05, or 0.32, or 0.16 etc, corresponding to the 68, 95, 99.7 rule) on an exam 1, this should set off alarm bells- if you double it and subtract it from 1, we get .95: corresponding directly to the 68,95,99.7 rule.

Thus, we can say that 108.8 is two standard deviations from the mean. Now we solve for the z score (which is 2)



Subbing in our values for the mean and sd









b) We dont actually need the value of a as it turns out, but we need to know the . So,



Solving this, we get

[2jzgte]

a) The transformed mean, , is equal to (because we know the original mean = 27.2)

We know that , so

Solving for gives us

Now, using the information we were given,

When you see 0.025 (or 0.05, or 0.32, or 0.16 etc, corresponding to the 68, 95, 99.7 rule) on an exam 1, this should set off alarm bells- if you double it and subtract it from 1, we get .95: corresponding directly to the 68,95,99.7 rule.

Thus, we can say that 108.8 is two standard deviations from the mean. Now we solve for the z score (which is 2)



Subbing in our values for the mean and sd









b) We dont actually need the value of a as it turns out, but we need to know the . So,



Solving this, we get

Thanks for the help, haven't encountered such a question before.

[cosine]

I honestly don't know why I cannot solve this attached image, I tried it multiple times with the same result

[cosine]

Someone also show me how to do this one too please

[The Mathemagician]

I'll give out hints for the first one: you can create two simultaneous equations to solve for A and k. One of them is based on the fact that there is a maximum at a particular point (hint: what's the derivative of a function at a maximum or minimum?). Also it may be useful to summarise what you tried here - someone might be able to tell you if you've made a mistake somewhere so you can learn from it.

For the second one you need to first find a formula for the area of that trapezium in terms of p and x. You will probably need to use trigonometry at some point.

[CDOGo]

Hi Guys,
I need help for a function p(t)= -20cos(2*pi*t/3)
I need to find the rate of change when p is a maximum WITHOUT using calculus.
The solutions provide sin (2*pi*t3)=1 to give t=3/4 seconds i have no idea how they got to sin without calculus. Can someone please shed some light thanks.


[odeaa]

Hi Guys,
I need help for a function p(t)= -20cos(2*pi*t/3)
I need to find the rate of change when p is a maximum WITHOUT using calculus.
The solutions provide sin (2*pi*t3)=1 to give t=3/4 seconds i have no idea how they got to sin without calculus. Can someone please shed some light thanks.


Well, technically it is calculus but because sin and cos are exactly half a cycle out of phase, when one has an intercept, the other will have a maximum and vice versa

Weird question, where did you find it?

[CDOGo]

Well, technically it is calculus but because sin and cos are exactly half a cycle out of phase, when one has an intercept, the other will have a maximum and vice versa

Weird question, where did you find it?

I found it in Heffernan 2006 exam 2. So if sin and cos are half a cycle how can the 20 (amplitude) cancel out?

[odeaa]

I found it in Heffernan 2006 exam 2. So if sin and cos are half a cycle how can the 20 (amplitude) cancel out?

The question is kinda worded weirdly, so I'm gonna assume you are trying to find the maximum? Because the rate of change at the maximum is 0, thats why its a maximum. The amplitude has no effect on the gradient at this point because it is 0 regardless of how steep  the gradient may be on either side. Are you sure you have copied the question exactly how it was in the exam?