Mathematics Question Thread

[jamonwindeyer]

Hey there, my teacher said that I should practice trial papers considering they are more difficult than HSC and that I should be aiming for 40% on my trial paper. However, my tutor said to stick to past HSC papers... What do you think?

Just to add, you should definitely be (eventually, after some or maybe a lot of hard work) aiming for more than 40% in your Trial papers! Everyone is different obviously, but you should never be aiming for a mark as low as 40%! Aim high!

[hansolo9]

Hi can someone explain how to do part b?
I really struggle with these maximum and minimum applications..
Thanks!!

[legorgo18]

Hi can someone explain how to do part b?
I really struggle with these maximum and minimum applications..
Thanks!!

Hey! For part b you differentiate the function from Part A, then make it=0 for stationary points. After solving do a sign table to check for min/max and you are good to go!

[hansolo9]

Hey! For part b you differentiate the function from Part A, then make it=0 for stationary points. After solving either do a sign table to check for min/max and you are good to go!

Oh wow! It was that simple lol
Thank you so much!!

[RuiAce]

Oh wow! It was that simple lol
Thank you so much!!

That process is (a bit boring but) very standard. Was there something else you thought you had to do?

[hansolo9]

That process is (a bit boring but) very standard. Was there something else you thought you had to do?

I thought you needed to do something like sub into the area formula.
I struggle with the volume ones where you have variable h and variable r, then find max V of a cone.

[RuiAce]

I thought you needed to do something like sub into the area formula.
I struggle with the volume ones where you have variable h and variable r, then find max V of a cone.

Max/Min problems are always related to the first derivative.

The concepts were more formally taught in the geometry of the derivative (as the Cambridge textbook calls it).

[hansolo9]

This is a really dumb question, isn't the volume 360 ?
Am I wrong, or is the question wrong?

[pikachu975]

This is a really dumb question, isn't the volume 360 ?
Am I wrong, or is the question wrong?

It is 420.

The area of the 2 top triangular prisms: 2 (1/2 * 6 * 6 * 5)
Area of bottom 2: 2 (1/2 * 8 * 6 * 5)

[chelseam]

This is a really dumb question, isn't the volume 360 ?
Am I wrong, or is the question wrong?

Hey! This is what I got:
Each of the triangles at the top would be 6x6x0.5x5, and since there are 2 the total volume is 180.
The bottom part of the shape is missing the perpendicular height but you can find that by using pythag, and that will give you 8cm. So the volume of the bottom part will be 8x12x0.5x5, which gives you 240.
180+240=420

[hansolo9]

Hey! This is what I got:
Each of the triangles at the top would be 6x6x0.5x5, and since there are 2 the total volume is 180.
The bottom part of the shape is missing the perpendicular height but you can find that by using pythag, and that will give you 8cm. So the volume of the bottom part will be 8x12x0.5x5, which gives you 240.
180+240=420

It is 420.

The area of the 2 top triangular prisms: 2 (1/2 * 6 * 6 * 5)
Area of bottom 2: 2 (1/2 * 8 * 6 * 5)

OHHH I SEE NOW. There's a pythagoras thing involved, didn't see that.
Thanks heaps

[hansolo9]

How would I do this?
(The correct answer is B)

[RuiAce]

How would I do this?
(The correct answer is B)

This question lacks information. I believe that they forgot to state that we have an isosceles triangle up the top. That was the only way I was able to make it work.

[Opengangs]

Yup, the only way I could make it work is that we have an iso. triangle.

[Fahim486]

For C) ii. I only put my answer as -0.00425 but the BOSTES answer says -0.004252436
Do it matter how many sig figs you put your answer to because the question doesn't really indicate how many sig figs or decimal places to put your answer