Alex C

A flat rate loan over 6 years at 12.75% per annum amounted to a repayment of $12 500.

How much was originally borrowed?

A lottery claims that 10% of tickets win a prize. How many tickets should you buy to be 50% sure of winning a prize?

This question is of binomial distribution/bernoulli trials. Can anyone help? I thought it might be:

solve for n in: nCr(n,r)*(0.1)^(r)*(.9)^(n-r) = .5

but I don't know what value to substitute for r.

Answer is 7.

Any help will be great. Thanks.

Differentiate x*ln(x)-x

Can anyone help me with this. I've used the product rule but I can't get to the answer.

The answer is ln(x).

If I have n number of amino acids, where n > 2, is there any mathematical formula to describe how many possible amino acids can be formed?

Thanks!

I'm having trouble with this calculus application question. Any help would be much appreciated.

A circular slick is increasing at a rate of 5 cm^2/s.

Find the rate of increase of the radius of the slick when the area is 400π cm^2.

Thanks.

One side of a rectangle is three times the other. If the perimeter increases by 2%, what is the percentage increase in the area?

This question requires linear approximation and percentage change. If anyone can help me in solving the question, it would be much appreciated. Thanks!

Can someone help me with this circular function question and explain what to do?

I've only just realised that I'm *not* allowed to evaluate sin π/6 to solve it, which is how I've been solving questions like this (I really should have read the question carefully, I guess).

The theory says that I have to use symmetry in the unit circle to help solve it, but I don't get what the textbook is saying.

Thanks.

Here is a question from Year 12 Chem that I can't figure out at all:

Ethylene glycol contains Carbon, Hydrogen, and Oxygen. Complete oxidation of 3.10g of Ethylene glycol produces 4.40g CO2 and 2.70g H2O. Determine the mass of O2 in the sample of Ethylene glycol.

I really have no clue where to start. I attempted to write out a chemical equation and find the mol of both CO2 and H2O, but then I wouldn't be able to then find the mol of Ethylene glycol because it may be unbalanced (hence, stoichometry couldn't be used — I think).

Any help at all is much appreciated! Thanks!

Hi, I have this question for Year 12 Chemistry and I don't know how to answer it:

In the acid-base reaction — 2Na (s) + 2H2O (l) <==> 2NaOH (aq) + H2 (g) — does Sodium act as an acid, a base or neither? Explain your choice.

I always thought that an acid-base reaction involves the transfer of protons (H+). I thought Na might have been a base (as it gains OH?), but then the product NaOH is also base, and hence it's not a conjugate pair, which has just confused me. Could someone please give an answer and explain as well?

Much appreciated and thanks in advance.

If some one wants to achieve/compete and be better than everyone else around him, is there are psychological term for it? Thanks.

Hi, just wondering if anyone can solve this maths problem.

If sin x° = sin 60° and 90°< x <180°, find x.

Thanks.

Hi,

My mac everyday is backing up my entire HDD and adds 80GB worth of data. It's really starting to eat into the space on my external hard drive. I know this isn't supposed to happen, because the Time Machine is only meant to back up files that I have updated. I have excluded several files (Virtual Disk Images worth 40GB that I frequently use) but it is still backing up files that I haven't touched in ages. Can someone help me fix this?

Thanks.

Hi. I have been looking forward to the iPad announcement for weeks now and I wanted to watch the launch video with Steve Jobs. However, I can only find live streams, which have all ended now (I missed the video sleeping as I live in Australia). Does anybody know a link with a full video of the announcement, that's not live? I've been looking everywhere but so far there's nothing. Thanks.

Hi,

My friend just installed Skype on her computer, but every time she tries to sign in or make an account, it says that it "cannot connect to server".

Could someone please help.

Thanks.

Hi,

I know this might sound like a stupid question, but does anyone know when Apple's WWDC will be held in 2010. I'm really looking forward to it!

Thanks.

Hi,

I just installed World Adventures, and I really want to play with a Sim that lives in China. How can I play with them, because whenever I do go to China in Edit Town, the Change Active Household is greyed out.

Thanks.

Hi. I'm thinking about buying a 32GB iPhone 3GS outright, and then use a prepaid account for calls. Will I be able to access the internet on a prepaid account, or am I better off just getting the iPhone on a plan? Thanks.

Could anyone please explain this to me?

Thanks.

My Sim's mother just died in the game. She lived in another household with some other family members. I wanted to place her grave in the graveyard, but I can't seem to find the actual gravestone. I changed the active household, went into her household and still I can't find it. I looked in the other Sims' inventory and even the Household Inventory. Where is it? Thanks.

I am writing an essay and I need to include that a character was 'hung over' the next morning. What's a proper phrase or term I could use rather than just 'hung over'.