# A LEVEL MATHEMATICS

### The Mailbox

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#### Things not looking too good for daughter in JC2 this year

 Posted by White Group Mathematics on April 12, 2018 at 4:45 AM comments (0)

Hi Mr Koh,

I came across your website while seeking someone to coach my daughter in H2 Maths. She is currently studying at TJC and will be taking her A Levels at the end of this year. At the present moment she has someone helping her with the subject but thus far she has failed in most of her tests and exams (since JC1). Quite frankly we are at a loss, because my daughter h...

#### Wiped out over tiny P&C problem

 Posted by White Group Mathematics on April 4, 2018 at 2:05 AM comments (0)

The problem is presented as follows:

A student entering a junior college has to offer 4 subjects, of which at least one must be chosen from the basket of science-related subjects ( Maths, Physics, Chemistry And Biology) and at least one being chosen from the basket of arts-related subjects ( Economics, Literature, History And Geography). How many subject combinations in all are available?

Here...

#### Finding equations of tangents parallel to y-axis, not sure how to proceed

 Posted by White Group Mathematics on January 12, 2018 at 12:20 AM comments (0)

Hello Mr Koh,

I recently encountered a problem in my holiday revision package which asked us to discover the equations of the tangents fo the curve  x^2- axy +y^2 =a  which are parallel to the y-axis. I managed to compute an expression via implicit differentiation for the gradient function, ie dy/dx = (ay-2x)/ (2y-ax) which I am not sure if it is correct; I also d...

#### Length of projection-confused with whether to use cross or dot product

 Posted by White Group Mathematics on November 28, 2016 at 4:40 AM comments (0)

Hi Mr Koh it's XXX. I have a question for you:

Why did the teacher use cross product instead of dot product? Thank you.

The way the respective dot and cross product results arise are attributed...

#### Need a maths tutor for final month before A Levels

 Posted by White Group Mathematics on September 28, 2016 at 4:50 AM comments (0)

Hi Mr Koh,

I chanced upon your website online and I'd really like to engage you as my private tutor. I'm currently a JC2 student studying in SAJC. I know this is very last minute, but I really do need the help; in summary,  I've tried really hard to work on my Math, however I really don't see any improvements in my grades and I...

#### Gradient of line and vectors

 Posted by White Group Mathematics on August 26, 2016 at 2:25 AM comments (0)

Hi Mr Koh,

#### Conics and applications of differentiation

 Posted by White Group Mathematics on February 13, 2016 at 9:05 PM comments (0)

I am having considerable difficulty grappling with this OCR problem. Could you kindly assist?

Student X

Worked it ...

#### Integrating cosec ^4 x wrt x

 Posted by White Group Mathematics on February 2, 2016 at 6:00 AM comments (0)

I was given some basic calculus revision questions to do for an undergrad module, but since there's nothing new in them, so I decided to give these questions an A-level tag. I've been working on them for a while now, but I'm stuck at this. Any help would be appreciated; I'm not particularly bothered if you want to post the answers as it's not an assessed homework, and I'm starting to get tired of these.

Student X

...

#### Poisson distribution approximated to normal distribution: Supply and demand problem

 Posted by White Group Mathematics on January 24, 2016 at 11:50 AM comments (0)

Sales of cooking oil bought in a shop during a week follow a Poisson distribution with mean 100. How many units should be kept in stock to be at least 99% certain that supply will be able to meet demand? Use normal approximation to Poisson distribution, if appropriate.

I have already approximated the distribution to Y ~ N (100, 100). Then, I have tried to use P(Y>y) = 0.99 . That didn't work so I...

#### Locus of points equidistant from x-y and x-z plane

 Posted by White Group Mathematics on November 4, 2015 at 10:10 AM comments (0)

Hi Mr Koh,