The Student Room Group

2012 Interview/MAT preparation

We were talking about this on the applicants page and I have seen this done in previous years so I figured it would healthy to do one this year.
The purpose of this thread is basically to test each other with Qs and to get help.
Two things:
-Please spoiler any solutions you may post. It really sucks when a question is spoiled for you by accidentally glancing at a solution.
-Can people please use their common sense when it comes to posing questions. Let's not have questions like: prove Maxwell's equations or some crazy contour integral.

Here are some I thought of that could work, apologies if they are too easy:
-Is πe<eπ\pi^{e}<e^{\pi}
-Prove that if the digital sum of a number is a multiple of 9 then it is divisible by 9.
-A sphere of unit radius is cut into two portions by a plane distance h from the centre. If the ratio of the bigger portion to the smaller portion is 2:1, show that h is a root of the equation 3h39h+2=03h^3-9h+2=0. Find h to two decimal places.

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Reply 1
For question 2 what is the digital sum of a number? I've never come across that before

And for question 3 I have a pretty good idea about how to go about it, I will attempt it then hopefully post a solution.
(edited 12 years ago)
Reply 2
The digital sum of 456 = 4+5+6 = 15
Reply 3
Original post by TheJ0ker
Question 1

Spoiler




Just lol
Reply 4
Original post by TenOfThem
The digital sum of 456 = 4+5+6 = 15


Thanks
Reply 5
Just testing

Spoiler

Original post by TenOfThem
The digital sum of 456 = 4+5+6 = 15

Re-read his question. He said if the digital sum of a number is 9, then the number itself is divisible by 9.

EDIT: Misunderstood your post, sorry about that.
(edited 12 years ago)
Reply 7
Original post by ben-smith
Just lol


What?
Reply 8
Original post by TheJ0ker
What?


Nothing, I just thought it was funny that someone aspiring to study maths at university uses that as a justification:tongue:
Reply 9
Original post by Farhan.Hanif93
Re-read his question. He said if the digital sum of a number is 9, then the number itself is divisible by 9.


She's explaining what the digital sum is.
EDIT: Just realised TenofThem is not a guy...
(edited 12 years ago)
So for example

For Q2

Spoiler



and extrapolate :smile:
(edited 12 years ago)
Original post by Farhan.Hanif93
Re-read his question. He said if the digital sum of a number is 9, then the number itself is divisible by 9.


yes I know ... not sure what your point is

that was a general e.g. explaining "digital sum" to Joker
Original post by TheJ0ker
Question 1

Spoiler


If you're looking for a hint, notice that πe=eelnπ\pi ^e = e^{e\ln \pi}.

It will come in handy at some point to consider the maximum value of lnxx\dfrac{\ln x}{x}.
Original post by TenOfThem
yes I know ... not sure what your point is

that was a general e.g. explaining "digital sum" to Joker

Oh my apologies, I thought you were trying to state that his proposition was false. My bad. :p:
Original post by Farhan.Hanif93
Oh my apologies, I thought you were trying to state that his proposition was false. My bad. :p:


ahhhhh

np :smile:
Original post by Farhan.Hanif93
If you're looking for a hint, notice that πe=eelnπ\pi ^e = e^{e\ln \pi}.

It will come in handy at some point to consider the maximum value of lnxx\dfrac{\ln x}{x}.


Hmmm, not quite what I had in mind.
Original post by ben-smith
She's explaining what the digital sum is.
EDIT: Just realised TenofThem is not a guy...


Looks down

Checks

agrees

:biggrin:
Original post by TenOfThem
Looks down

Checks

agrees

:biggrin:


Would it be out of line to ask for pics?:tongue:
Original post by ben-smith
Hmmm, not quite what I had in mind.

Comes out quite nicely that way.
Original post by Farhan.Hanif93
Comes out quite nicely that way.


I'm sure it does, I like my way:colone:

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