VCE General & Further Maths Question Thread!

[jeanweasley]

Just a question regarding constraints in linear graphing:

If the point is a decimal and the situation you're talking about involves whole numbers, do you round up or round down?

Eg. If the point is (21.6, 12.3)

Cheers

[Stick]

It depends on what the variables actually are. In most practical cases, you'll be rounding down as the items are discrete. However, when simply dealing with numbers, you'll round to the nearest integer. Check the question too, since it may specify what to do.

[jimmy22]

Hi,
If a 1 mark question stated, 'Give one reason why a dummy activity may be used in a network,"

Would, " A dummy activity may be used in a network to ensure that all predecessor activities are properly accounted for," be sufficient for the mark?

Thanks

[BLACKCATT]

Asking a question for a friend of mine

From a point, A, due north of a tower, the angle of elevation to the top of the tower is 45◦.
From a point, B, 100 m on a bearing of 120◦ from A, the angle of elevation is 26◦. Find the
height of the tower.

can someone help with this question?

[aestheticatar]

can someone help with this question?

I tried roughly sketching it out first. I've attached the bird's eye view and side views of the scenario to help.
If you follow my sketch:

Let height of tower = x metres
Let horizontal length from tower to B = y metres

As angle of elevation to top of tower from A is 45 degrees, we know horizontal distance from tower to A is also x metres (equal to height of tower).

As angle of elevation to top of tower from B is 26 degrees, we can use SOHCAHTOA to calculate that:
tan(26) = x/y
Transpose to find y in terms of x:
y = x/tan(26)

Use cosine rule on triangle (bird's eye view) to determine value of x:
y^2 = x^2 + 100^2 – 2(x)(100)cos(60)
(x/tan(26))^2 = x^2 + 100^2 – 2(x)(100)cos(60)

Solve for x using CAS:
x = 42.40, -73.61

x must be 42.4 metres as x > 0
Thus height of tower being x, is 42.4 metres tall.

Hope I helped!
P.S. Sorry for the dodgy drawing!

[BLACKCATT]

thanks! that helped a lot 

[jeanweasley]

Hi,

I need help with this question.

I have been given the matrix q and the matrix qrx and the question asks me to solve for x. How would I do this? I know that I have to use the inverse somewhere but if X and R are unsolved, how would I do this?

Here's the actual question.

Given Q  (2x2) no from left to right, first row then second is -2,4,3 and -2. and QRX is (2x1) top to bottom -24 and 32.

[Yacoubb]

Hi,

I need help with this question.

I have been given the matrix q and the matrix qrx and the question asks me to solve for x. How would I do this? I know that I have to use the inverse somewhere but if X and R are unsolved, how would I do this?

Here's the actual question.

Given Q  (2x2) no from left to right, first row then second is -2,4,3 and -2. and QRX is (2x1) top to bottom -24 and 32.

What answer did you get?

I did a method but I don't know if my answer is right

[lolipopper]

Hi,

I need help with this question.

I have been given the matrix q and the matrix qrx and the question asks me to solve for x. How would I do this? I know that I have to use the inverse somewhere but if X and R are unsolved, how would I do this?

Here's the actual question.

Given Q  (2x2) no from left to right, first row then second is -2,4,3 and -2. and QRX is (2x1) top to bottom -24 and 32.

i dont get what you are asking. is this question in the vcaa exams or essentials further book?

[Insa]

Hey guys Could anyone please help me with question in relation to networks? Thank you.

[RKTR]

E won a match. the opponent who lost to E also only won a match. therefore E must have defeated A.

[Zealous]

Do we need to connect the dots on a time series if we plot one? Or can we leave them disconnected?

[Stick]

Connect them together.

[Yacoubb]

Would the following explanations be appropriate (they're for linear regression): i've just used example figures.

Coefficient of determination
87.56% of the variation in arm span can be explained by variation in height.

Describing a relationship:
From the scatterplot, it can be seen that there is a strong, negative linear relationship between number of errors on a test and the period of time spent studying, with no outliers.

Gradient:
On average, the final weight of Jane decreases by 1.44kg for every additional day spent working out.

Y-intercept:
On average, Jane's final weight at the start of the weight-loss program, is 96kg.

^ Are these templates for such questions okay? Thanks!

[jimmy22]

They look good to me.

The only thing that i might've added is for the Coefficient of determination you could also say in the next sentence, "12.46% of the variation in arm span can be explained by other factors such as ......."

Not sure if it's necessary though.