PSLE Prelim Qn again

[Observer]

i rem Ali, bala, Susan, mary, xiaoming, Mr yakki, yakko and miss lala....

 

why got yakki and yakko?

 

u in japanese lesson ah?

[Observer]

last time use Ali, Ah Meng..... last time use apple, ball (ribbon!!) then last time where got twisting of words

 

tts y if i still primary school now sure buang...dun even know what they asking

[Observer]

Not forgetting Ali, Siew Hua, Mary, Bala, Fatimah....who did I miss......

 

So what we have now?

 

They v multi racial..sure got all 4 races in the problem sums section ha

[Jagash]

RGS Primary 2009 PSLE Math Prelim Paper 2 Q9

 

Tricia has some pink, red and yellow ribbons. 1/3 of them are pink ribbons. Four fewer than 1/3 of the remainder are red ribbons. How many pink ribbons does Tricia have?

 

 

How to do bros, even i see the Ans also i don't know how to do. Am i stupid or wat

 

The answer is:

 

Pink = 15

Red = 6

Yellow = 24

[Ahseng]

The answer is:

 

Pink = 15

Red = 6

Yellow = 24

 

 

u got the model ans. erm can teach me how to get? draw diagram?

[Kiadaw]

yea bro i tink there is more than one solution too. Lol, i'm here to get enlightened myself. Tried this cos my wife say psle nowadays very hard, i juz googled and stumbled onto the qn. Seems like RGS "eliteness" = confusing questions? from the look of the question i tink the graph(diagram) is part of the solution.

 

Anyone can use P6 way to do? diagram form. [laugh]

Or this is seriously flawed qn and dun waste time to attempt

 

Got late for work trying to solve this problem & then to explain to others the flaws & how to interpret the "angmoh".

 

Haha. Thankfully I am engineer & use maths quite often, so never "lose face". hehe.

 

 

 

ANyway, those interested in Math should see the 4 part series of the history of maths.

 

Very interesting. Do you know that the number "0" zero been known to exist only like the since the 4th century or something, & negative number much later. Before that, there was no concept of zero!

 

It also have many stories how much ancient people use ingenius method to calulate complex sums & equations. Let us know who is resposible for the invention of things like calculus, trigo, how the ancient Eyptians make perfect right angle for the pyramid, how they know how many bricks are need etc.

Edited September 29, 2010 by Kiadaw

[Ferraricalifornia]

Got late for work trying to solve this problem & then to explain to others the flaws & how to interpret the "angmoh".

 

Haha. Thankfully I am engineer & use maths quite often, so never "lose face". hehe.

 

 

 

ANyway, those interested in Math should see the 4 part series of the history of maths.

 

Very interesting. Do you know that the number "0" zero been known to exist only like the since the 4th century or something, & negative number much later. Before that, there was no concept of zero!

 

It also have many stories how much ancient people use ingenius method to calulate complex sums & equations. Let us know who is resposible for the invention of things like calculus, trigo, how the ancient Eyptians make perfect right angle for the pyramid, how they know how many bricks are need etc.

 

 

 

yah....those were the times where great concepts and theories were invented and thought of.....

 

what we're doing now is to improve things which were invented.....and not coming out with more theories of our own.....

[Jagash]

Bro, I do not know how to attach the diagram.

Let me explain and hope you understand.

Pink is one third, so draw 1 box.

Hence red and yellow are the remainder two thirds, so 2 boxes.

 

Next, sincered is 4 fewer than the remaining one third, you will need to sub-divide each box into 3 smaller boxes.

So Pink now becomes 3 boxes, Yellow is 4 boxes + 4 and red is 1 box + 1 box less 4.

 

From this logically, each box must definitely be equal to more than 4 units. Since the next number is 5, lets assume that this is correct first and do trial and error test.

Using 5 as the unit of each box, you have:

Yellow = (4X5) + 4 = 24

Red = (1X5) + (5-4) = 6

Pink = (3X5) = 15

 

If the question does not specify the quantity for any of the colours or the total quantity, there can be many other correct answers but this answer assumes the lowest possible total quantity.

 

Hope my explanation is clear.

 

 

[Kxbc]

very clear. understand. thank you. you can be a tuition teacher.

[Requiemdk]

How can that be the lowest possible when 9 Pink, 2 Red, 16 Yellow ribbons work just as well?

 

One might just as well draw 1 circle for the pink ribbons, then for the remaining ribbons, red = 1 box - 4, yellow = 2 boxes + 4 where the 3 boxes add up to 2 circles. Do trial and error for the number of red ribbons. If there's only 1 red ribbon, then the number of pink ribbons is not a whole number. Setting the number of reds to 2 gives you the above answer. In fact, setting the number of reds to 0 works equally well.

 

When you subdivided the boxes for the number of reds and yellows in your solution, an implicit assumption was already made that 3 must be a common divisor of the number of reds, yellows and pinks. Nowhere in the question do I see any grounds for this assumption...

 

Edit: Free tip - don't take model answers for granted, even if the papers are from supposedly top schools. I've seen plainly wrong mathematics being taught in schools and worse, mathematically WRONG questions being set for exams. It isn't that uncommon either... Already spotted at least 3 such incidents this year.

Edited September 29, 2010 by Requiemdk

[Pokyman]

wah piang, so cheem ... i worry when my sons PSLE turn comes

 

Sometimes wonder how i got a job in Finance ... lol

[Kxbc]

I think Finance can use laptops and calculators without need to draw boxes.

[The_Bear]

I think Finance can use laptops and calculators without need to draw boxes.

 

How the F did I pass my PSLE??

[Kxbc]

You passed? I didn't. Remember last time got Pri 8?

[Kiadaw]

Edit: my bad, make a mistake in my calculation. Sorry.

Edited September 29, 2010 by Kiadaw

[Mightymito]

Dude. there are 4 unknowns . Total (T) , red® , pink(p) , yellow (y)

 

total number of equation you need to solve the problem is equal to the total number of unknowns.

 

first statement(condition) you get one equation. Second statement(condition) you can get two equations.

 

You are one equation short for a solution.

 

This is basic algebra.

 

 

[The_Bear]

You passed? I didn't. Remember last time got Pri 8?

 

I got A-stars!

 

Primary 8 + Sec 5, add repeat and you have a 20 years old 'O'-level candidate

[Johnnylim]

So wat is the correct answer