O-Level Additional Math

[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

[Vanilla Cake]

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

Hi cchew,
Thanks for the link. Will place order for them.

[midnightspark]

Hi,


Just asking some sec 2 maths questions, please help


1)
A rectangle of sides x cm and y cm has an area of 72 cm2. Another rectangle of sides (x+1.5) and (y-4)cm has the same area. Find the values of x and y.

2)
When 5 is added to both the numerator and denominator of a fraction, the result becomes 1/2. When 1 is subtracted from both the numerator and the denominator, the fraction becomes 1/5. Find the fraction.

3)
The scale of map X is 1: x and the scale of map Y is 1:y. If the same distance is represented as 5cm on map X and 7.5cm on map Y, calculate the ratio x:y.

Thanks.

[CoffeeCat]

midnightspark:

Hi,


Just asking some sec 2 maths questions, please help


1)
A rectangle of sides x cm and y cm has an area of 72 cm2. Another rectangle of sides (x+1.5) and (y-4)cm has the same area. Find the values of x and y.

2)
When 5 is added to both the numerator and denominator of a fraction, the result becomes 1/2. When 1 is subtracted from both the numerator and the denominator, the fraction becomes 1/5. Find the fraction.

3)
The scale of map X is 1: x and the scale of map Y is 1:y. If the same distance is represented as 5cm on map X and 7.5cm on map Y, calculate the ratio x:y.

Thanks.

For qns 2, use algebra.
let the original fraction be x/y.
(x+5)/(y+5) = 1/2
cross multiplying, 2x + 10 = y+ 5
2x + 5 = y
(x-1)/ (y-1) = 1/5
5x - 5 = y - 1
......

For qns 1
xy = 72
(x+1.5)(y-4) = 72
let y= (72/x) and substitute . You will get a quadratic equation after multiplying the whole equation by x.

For qns 3,
5x = 7.5y
x/y = 7.5/5 = ...

hmmm too busy to give you full solutions. hope this helps.

[midnightspark]

CoffeeCat:

midnightspark:

Hi,


Just asking some sec 2 maths questions, please help


1)
A rectangle of sides x cm and y cm has an area of 72 cm2. Another rectangle of sides (x+1.5) and (y-4)cm has the same area. Find the values of x and y.

2)
When 5 is added to both the numerator and denominator of a fraction, the result becomes 1/2. When 1 is subtracted from both the numerator and the denominator, the fraction becomes 1/5. Find the fraction.

3)
The scale of map X is 1: x and the scale of map Y is 1:y. If the same distance is represented as 5cm on map X and 7.5cm on map Y, calculate the ratio x:y.

Thanks.

For qns 2, use algebra.
let the original fraction be x/y.
(x+5)/(y+5) = 1/2
cross multiplying, 2x + 10 = y+ 5
2x + 5 = y
(x-1)/ (y-1) = 1/5
5x - 5 = y - 1
......

For qns 1
xy = 72
(x+1.5)(y-4) = 72
let y= (72/x) and substitute . You will get a quadratic equation after multiplying the whole equation by x.

For qns 3,
5x = 7.5y
x/y = 7.5/5 = ...

hmmm too busy to give you full solutions. hope this helps.

Thanks for the solution!

[SKT]

Hi,


LCM of A&B is 4x², B&C is 12x³, A&C is 6x³. Find all possible expressions C.