• Best of luck to the class of 2020 for their HSC exams. You got this!
    Let us know your thoughts on the HSC exams here
  • Looking for HSC notes and resources?
    Check out our Notes & Resources page

Australian Maths Competition (1 Viewer)

kurt.physics

Member
Joined
Jun 16, 2007
Messages
847
Gender
Undisclosed
HSC
N/A
Westpac Maths Comp marathon

okay, so the Westpac maths comp (aka AMC) is coming up so for those who are doing it or just want do some hard maths problems this "marathon" is a kind of warm up =)

So to get the ball rolling, i will post up a westpac maths question and who ever correctly solves it gets to post up another westpac question and then who ever solves that posts up another westpac question etc. We should start off fairly easy and increase the difficulty of the questions as the marathon progresses.

If you dont have any of the papers i have posted them here:

http://community.boredofstudies.org...australian-maths-competition.html#post4478693

Or if you have some of the questions from an earlier year feel free to post them =)

QUESTION 1

A rectangle has its length 25 times its width. What is the ratio of
its perimeter to the perimeter of the square of the same area?

-(A) 13 : 5 (B) 13 : 10 (C) 5 : 1 (D) 51 : 20 (E) 51 : 10



Ready, Steady, GO!
 

d3st1nyLiang

Premium Member
Joined
Jan 23, 2009
Messages
513
Gender
Male
HSC
2011
Re: Westpac Maths Comp marathon

is it a)?

A lucky number is a positive integer which is 19 times the sum of its digits. How
many different lucky numbers are there?
 

clue444

Member
Joined
Oct 1, 2008
Messages
100
Gender
Male
HSC
2010
The 2008 answers are in chinese damn lol. Thanks heaps Kurt!
 

shaon0

...
Joined
Mar 26, 2008
Messages
2,049
Location
Guess
Gender
Male
HSC
2009
Re: Westpac Maths Comp marathon

is it a)?

A lucky number is a positive integer which is 19 times the sum of its digits. How
many different lucky numbers are there?
I don't know if my methods right:
By using the conditions in the questions. It's easy to deduce that the number isn't a 1,2 or 4 digit number. So it's a 3 digit no.
Let the digits be as follow: 100 digits in hundreds place, 10 digits in 10s place and 10 digits in 1's place.

Alternatively, I think you can just go:
Z*19=ABC where {Z,A,B,C E Z}
So say for: a no. which has digits summing to 6 is:
6*19=114

Thus, Z is in between 5 and 16
So 10 numbers.
 
Last edited:

kurt.physics

Member
Joined
Jun 16, 2007
Messages
847
Gender
Undisclosed
HSC
N/A
Re: Westpac Maths Comp marathon

I don't know if my methods right:
By using the conditions in the questions. It's easy to deduce that the number isn't a 1,2 or 4 digit number. So it's a 3 digit no.
Let the digits be as follow: 100 digits in hundreds place, 10 digits in 10s place and 10 digits in 1's place.

Alternatively, I think you can just go:
Z*19=ABC where {Z,A,B,C E Z}
So say for: a no. which has digits summing to 6 is:
6*19=114

Thus, Z is in between 5 and 16
So 10 numbers.
Close, the actual answer is 11 :|

Here is the solution:

As shaon showed, the lucky number must be a 3 digit number.

Suppose the number is abc.

Then , we have:



ie



Note that as b and c are the ten's digit and unit's digit respectively, then



So the maximum is and therefore the maximum a is





So we must only check for

For a = 1, we have
For a = 2, we have
For a = 3, we have , and there are no other solutions.

Hence there are exactly 11 lucky numbers, namely,


We should post up easier questions first just to get the marathon going =)
 

kurt.physics

Member
Joined
Jun 16, 2007
Messages
847
Gender
Undisclosed
HSC
N/A
Re: Westpac Maths Comp marathon

PROBLEM 3

Tina has a large number of 1 × 2 × 6 rectangular blocks. She wants
to make a solid cube out of the blocks. What is the smallest number
of blocks she needs?

(A) 6 (B) 12 (C) 18 (D) 36 (E) 144
 

shaon0

...
Joined
Mar 26, 2008
Messages
2,049
Location
Guess
Gender
Male
HSC
2009
Re: Westpac Maths Comp marathon

Close, the actual answer is 11 :|

Here is the solution:

As shaon showed, the lucky number must be a 3 digit number.

Suppose the number is abc.

Then , we have:



ie



Note that as b and c are the ten's digit and unit's digit respectively, then



So the maximum is and therefore the maximum a is





So we must only check for

For a = 1, we have
For a = 2, we have
For a = 3, we have , and there are no other solutions.

Hence there are exactly 11 lucky numbers, namely,


We should post up easier questions first just to get the marathon going =)
Yeah it is 11. lol. I counted my solutions in between 5 and 16 incorrectly.
 

girish

New Member
Joined
Aug 3, 2009
Messages
1
Gender
Male
HSC
N/A
Here is 2008 q + a and 2006 answers.
Hi Kurt,

Thanks for these papers and answers for AMC. For some years there was just the answers and not teh solution methods as such. Can you send these also if you have, say for 2008, 2006,2005,2004 and 2003? I am taking part inthe JUnior level. Thanks.:)
 

Aquawhite

Retiring
Joined
Jul 14, 2008
Messages
4,950
Location
Gold Coast
Gender
Male
HSC
2010
Uni Grad
2013
I think I am meant to be in this >_>... I'm really not in the mood for doing this since the Trials are just around the corner and all I've focused on is the syllabus and not really extra curricular (interesting maths ...).

Ima probably end up with just a participation or a credit if I'm lucky probably. Not that I care XD
 

nerdsforever

hsc zomg
Joined
Jan 10, 2008
Messages
464
Gender
Female
HSC
2010
Re: Westpac Maths Comp marathon

Cheers kurt! you're awesome. what do you usually get in the maths comp?

Here's a new question.

A sequence {u1, u2, . . . , un} of real numbers is defined by




for n≥ 3.


What is u2008?
(A) −√2
(B) 2008(√2 − 2008pi)
(C) 1003√2 − 1004pi
(D) pi
(E)√2
 

kurt.physics

Member
Joined
Jun 16, 2007
Messages
847
Gender
Undisclosed
HSC
N/A
Re: Westpac Maths Comp marathon

Cheers kurt! you're awesome. what do you usually get in the maths comp?

Here's a new question.

A sequence {u1, u2, . . . , un} of real numbers is defined by





for n≥ 3.


What is u2008?
(A) −√2
(B) 2008(√2 − 2008pi)
(C) 1003√2 − 1004pi
(D) pi
(E)√2


















We see the pattern emerging s.t.







So consider the pattern in modulo 6.

The 2008th term will be equivalent a specific residue modulo 6 and hence we can determine which term the 2008th term is equivalent to



 

kurt.physics

Member
Joined
Jun 16, 2007
Messages
847
Gender
Undisclosed
HSC
N/A
Re: Westpac Maths Comp marathon

Problem 5

The sum of three numbers is 4, the sum of their squares is 10 and the sum of their
cubes is 22. What is the sum of their fourth powers?
 

kurt.physics

Member
Joined
Jun 16, 2007
Messages
847
Gender
Undisclosed
HSC
N/A
I re-found the website which has the papers =)

AMC papers (this is in Chinese ;P)

AMC papers (in English)

(for the second link you have to click on the "Downloads" tab to the left)
 
Last edited:

appl3licious

New Member
Joined
Aug 4, 2009
Messages
5
Gender
Female
HSC
2012
Australian Mathematics Competition

Hi everyone~:)
i was just wondering if anyone had the AMT solutions for year 2002 - 2006 (intermediate division)???
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top