O-Level Additional Math

[Vanilla Cake]

Muffins:

Just a question to ask. For my exam, I had gotten a question like this:


a) Express 756 in its index form

b) Hence, find the value k where 756k is a perfect square.

I had gotten part a) correct, but I had put 2⅓ for part b), but they marked me wrong, saying that the answer was 21. Could anyone explain why? Thanks.

756=2²x3³x7
(a) 756 in its index form = 2²x3³x7

Perfect square =2²x3⁴x7²
k = 3x7 = 21

(b)Value of k where 756k is a perfect square = 21

Pls do not :offtopic:

[atutor2001]

Muffins:

Just a question to ask. For my exam, I had gotten a question like this:


a) Express 756 in its index form

b) Hence, find the value k where 756k is a perfect square.

I had gotten part a) correct, but I had put 2⅓ for part b), but they marked me wrong, saying that the answer was 21. Could anyone explain why? Thanks.

There is probably a requirement in the question that \"k is a whole number, find the smallest value of k\", which is why your answer is not acceptable

[CoffeeCat]

OK Lor:

Hi CoffeeCat,


Thanks for Q1. Please help to comment on Q2:

f(x) = 9/(1+cos2x) + 25/(1-cos2x) = 9/[2(cos x)^2] + 25/[2(sinx)^2]
= [9(sec x)^2 + 25(cosec x)^2] / 2
f'(x) = 9[(sec x)^2](tan x) - 25[(cosec x)^2](cot x) = 0
9[(sec x)^2](tan x) = 25[(cosec x)^2](cot x)
(tan x)^4 = 25 / 9
tan x = (5/3)^(1/2); cos x = (3/8 )^(1/2), sin x = (5/8 )^(1/2).
Least possible value of f(x) = [9(8/3) + 25(8/5)] / 2 = 32 ?

Thanks.

sounds correct to me ...

[OK Lor]

Hi 高人 CoffeCat,


Thanks.

[Muffins]

atutor2001:

Muffins:

Just a question to ask. For my exam, I had gotten a question like this:


a) Express 756 in its index form

b) Hence, find the value k where 756k is a perfect square.

I had gotten part a) correct, but I had put 2⅓ for part b), but they marked me wrong, saying that the answer was 21. Could anyone explain why? Thanks.

There is probably a requirement in the question that \"k is a whole number, find the smallest value of k\", which is why your answer is not acceptable

Hi atutor2001, this was actually the exact question itself,, nothing missed out.... :sad:

[Muffins]

Vanilla Cake:

Muffins:

Just a question to ask. For my exam, I had gotten a question like this:


a) Express 756 in its index form

b) Hence, find the value k where 756k is a perfect square.

I had gotten part a) correct, but I had put 2⅓ for part b), but they marked me wrong, saying that the answer was 21. Could anyone explain why? Thanks.

756=2²x3³x7
(a) 756 in its index form = 2²x3³x7

Perfect square =2²x3⁴x7²
k = 3x7 = 21

(b)Value of k where 756k is a perfect square = 21

Pls do not :offtopic:

Hi VC, thanks for the answer, but I wanted to know the explanation as to why my answer was not allowed. It is, in fact, a smaller value than 21, which still makes 756 a perfect square.... TIA.

[Vanilla Cake]

Hi Muffins,

Sorry, I don't know how to explain.Better go and ask your teacher when school reopens.


BTW,my younger sister is taking part in http://www.acs.sch.edu.sg/acs_indep/announcements.php?id=93 for All Singapore Primary Schools 2010.Do you know whether ACSI sell the worked solutions for the past years' questions of Mathlympics?Do let us know your findings.
Thanks.

[Muffins]

Getting right on that now.... http://www.postimage.org/

[Muffins]

Hi VC, I have found out that ACS(I) has sent out questions from the preliminary round of Mathlympics 2009 to the participating schools, so I hope that helps. Gonna find more now…

[cchew]

Vanilla Cake:

BTW,my younger sister is taking part in http://www.acs.sch.edu.sg/acs_indep/announcements.php?id=93 for All Singapore Primary Schools 2010.Do you know whether ACSI sell the worked solutions for the past years' questions of Mathlympics?Do let us know your findings.
Thanks.

You can get from HotHouse Educational Services Pte Ltd
http://www.econnections.com.sg/index1.htm