VCE Specialist 3/4 Question Thread!

[brightsky]

Let x be the profit made by participant. Construct probability table for X, letting c be the cost of entry. Then solve E(X)=0 for c.

[hyunah]

why did they divide by 1 - (1/2)^6? what does it mean?

[kinslayer]

why did they divide by 1 - (1/2)^6? what does it mean?

(1/2)^6 is the probability that the participant guesses all six tosses correctly. The expected profit for the participant is:

(1/2)^6 * (profit if participant makes all guesses correctly) + (1 - (1/2)^6) * (profit if participant gets a toss wrong)

You should get answer D.

[hyunah]

they divided by the probability that the participant gets it wrong on the toss
from the companies perspective
they gain profit if the participants gets it wrong
so to break even means E(x) = 0

how do we calculate E(x) = what's the formula?

[keltingmeith]

they divided by the probability that the participant gets it wrong on the toss
from the companies perspective
they gain profit if the participants gets it wrong
so to break even means E(x) = 0

how do we calculate E(x) = what's the formula?

While everyone here should be able to answer this, probability questions are best left in the methods forum.

Calculating E(X) for discrete data is given by - this should be in your methods textbook, and is also on the methods formula sheet.

[Brunette15]

Does anyone have any suggestions for unit 3 revision? Should I start going through random practice exam questions or just chapter reviews? 

[keltingmeith]

I've said it before, I'll say it again - chapter reviews are pointless for exam study. You're best to jump into exam-style questions, and use the actual chapters to revisit topics you're not sure about.

[hyunah]

can someone please help with part b) please?

so what ive done so far is sqrt2 <equal to mod z < equal to 3
to find s<equal to x^2 +y^2 < equal to 9
and then im stuck

[Conic]

Not really a systematic way of getting the answer, but you can plot points on your diagram for the region:



The points that have x and y as integers that are in the region are -1+i, -1+2i, and -2+2i.

[Brunette15]

Hi everyone,
I was just wondering if we use specialist knowledge in a methods exam , such as proving things with second derivatives will we lose marks?

[Mieow]

Can someone please help me with these two questions:

The rate of change of the gradient at any point is given by x^2 + x − 1. Find the equation of the curve
that passes through (2, 1) if the tangent to the curve makes an angle of 45° with the positive direction
of the x-axis when x = 1.

and

The number of bacteria in a colony increases according to the differential equation . If the
number increased from 1000 to 4000 in 10 days, how much longer before there are 10 000 bacteria
present?

[lzxnl]

Can someone please help me with these two questions:
and

Here's an outline of how to do the first one.
They give you the rate of change of the gradient, so if you integrate this, presumably you get the gradient. Then they tell that when x=1, the tangent to the curve makes an angle of 45 degrees with the positive direction of the x axis, aka gradient = 1. Try and use that to find the integration constant for the gradient. Then, when x=2, y=1. Use that.

As for the second one with dN/dt = kN, attempt to solve it and see what happens. Use the fact that the population quadruples in ten days.

[lolalol]

Hey guys can anyone please explain why this happens during integration? Am I totally missing something haha?
(see attached photo - aware that I forgot the +c at the end of the last line btw)
Thanks in advance!

[Conic]

Both are essentially the same:

[LiquidPaperz]

what sort of grade should i be looking to be getting in methods to do well in specialist next year? as in 38 raw +

I go to a public school, if Melbourne High was 10/10, we'd be around 7.5/10, just to give a comparison in terms of VCE scores from last year.

Should i be grasping every topic with ease? is that some sort of indication