Standard Math Q+A Thread

[RuiAce]

need help with a question, its somewhat simple just wanted to know ways to do it easy.
The question is the image below.

Can't get easier than that

[Shadowxo]

need help with a question, its somewhat simple just wanted to know ways to do it easy.
The question is the image below.

Or, alternatively, since they're similar the ratio of the sides is the same
CB/15 = 24/16
Or, CB/24 = 15/16
(Yes Rui it can get easier. Also, I think you meant cos instead of sin)

[Aaron2230]

Can u help me with this aswell, i thought it was (B) but its (A) how?

Martine buys stationary which costs $104.50 including GST. Because she works
for a charity she can claim the 10 % GST back from the taxation office. How
much GST can she claim?

(A) $9.50 (B) $10.45
(C) $95.00 (D) $94.05

[RuiAce]

Or, alternatively, since they're similar the ratio of the sides is the same
CB/15 = 24/16
Or, CB/24 = 15/16
(Yes Rui it can get easier. Also, I think you meant cos instead of sin)

Similar triangles isn't really easier... they're the same. Saying by inspection we have similar ratios isn't endorsed in any HSC maths course without at minimal, reference to similarity.

But yeah, thanks for picking up on the typo

Can u help me with this aswell, i thought it was (B) but its (A) how?

Martine buys stationary which costs $104.50 including GST. Because she works
for a charity she can claim the 10 % GST back from the taxation office. How
much GST can she claim?

(A) $9.50 (B) $10.45
(C) $95.00 (D) $94.05

[Aaron2230]

Help with a question:

A car's petrol consumption (C) in litres/lOOkm can be estimated by using the formula: c=o.01s2 - s+33
where S is the speed (in km/h) at which the car is being driven.

What is the change in petrol consumption if the speed at which a car is being driven increases
from 60km/h to 80km/h?

(A) A decrease of 8 L/100km
(B) An increase of 8 L/100km
(C) A decrease of 17 L/100km
(D) An increase of 13.2 L/100km

[Natasha.97]

Help with a question:

A car's petrol consumption (C) in litres/lOOkm can be estimated by using the formula: c=o.01s2 - s+33
where S is the speed (in km/h) at which the car is being driven.

What is the change in petrol consumption if the speed at which a car is being driven increases
from 60km/h to 80km/h?

(A) A decrease of 8 L/100km
(B) An increase of 8 L/100km
(C) A decrease of 17 L/100km
(D) An increase of 13.2 L/100km

Hi!

Hope this helps

[Aaron2230]

Hi!

Hope this helps

yeah it did thanks just wanted to make sure i was doing it right 

[Adammurad]

A fair coin is tossed 16 times.
a. Find the mean and standard deviation of the number of heads
appearing.
b. Show that the probability of the number of heads lying within two
standard deviations of the mean is approximately 0.95.
Anyone have a solution?

[RuiAce]

A fair coin is tossed 16 times.
a. Find the mean and standard deviation of the number of heads
appearing.
b. Show that the probability of the number of heads lying within two
standard deviations of the mean is approximately 0.95.
Anyone have a solution?

I am not sure where this is from as this is not taught in the HSC general courses.

[emilybrooks99]

could someone please walk me through how to do simultaneous equations with the elimination method. thank you!

[EEEEEEP]

could someone please walk me through how to do simultaneous equations with the elimination method. thank you!

The elimination method of solving systems of equations is also called the addition method. To solve a system of equations by elimination we transform the system such that one variable "cancels out" after adding...

Let say.... we have two equations..
x + y = 5              eq 1
2x -y = 10...        eq 2

1. Add eq 1 and 2
3x= 15......x =5

Sub x = 5.. into any of the above and we get y = 0.
Edit sorry...I did the wrong method....

[Natasha.97]

Hi!

This is a simultaneous equation involving 3 variables



Hope this helps

Edit: Formatting

[Lachlan Morley]

Hi guys,

Quick question about the Least Square line of best fit

When i find the gradient for the formula, sometime i would round off to diffrent decimal places then the answers for th standard deviations and amount of decimal places for the gradien

This , as a result, make my final equation slightly out to what the anwers have

If my equation is slightly out but i have shown full working, would i still get full marks and if not how can i ensure i round to the same decismals as the answers will

Thanks

[jamonwindeyer]

Hi guys,

Quick question about the Least Square line of best fit

When i find the gradient for the formula, sometime i would round off to diffrent decimal places then the answers for th standard deviations and amount of decimal places for the gradien

This , as a result, make my final equation slightly out to what the anwers have

If my equation is slightly out but i have shown full working, would i still get full marks and if not how can i ensure i round to the same decismals as the answers will

Thanks

You would almost certainly get full marks as long as it is very close, if you are rounding you should try to take a few extra places than you'll actually need at the end! This will keep things more precise (not rounding at all, where possible, is always the best way)

[Lachlan Morley]

You would almost certainly get full marks as long as it is very close, if you are rounding you should try to take a few extra places than you'll actually need at the end! This will keep things more precise (not rounding at all, where possible, is always the best way)

ok great thanks jamon, for you online HSC holiday video lectures would you be able to do a sction on least sqaure line of best fit ?