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PSLE Prelim Qn again

Ahseng

By Ahseng,
in Lite & EZ

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Jagash

Jagash

Neutral Newbie

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.

 

Make sense. If you are using the modelling method that is thaught in school, the only way to get one third of the remainder is to sub-divide each box into 3.

Anyway if this type of questions are set in the exam, they will have to accept any answer that can solve the problem. I remember one year they gave free marks to all PSLE students for a couple of the questions.

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Dogbert1973

Dogbert1973

Clutched

I also got PSLE question:

 

Daddy salary is X1, want to buy car (X2) and house (X3), but X2+X3 >X1

Old Friend want to borrow money Y1, IRAS wants Y2, SP Power wants Y3. Y1+Y2+Y3 = X1 * 0.5

Z1 (Mummy every night got headache) + Z2 (Female colleague just started work and is 21 yrs old with 36C assets.). Assume Company always got overtime T+3

Solve for X, Y and Z

 

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The_Bear

The_Bear

Turbocharged

I also got PSLE question:

 

Daddy salary is X1, want to buy car (X2) and house (X3), but X2+X3 >X1

Old Friend want to borrow money Y1, IRAS wants Y2, SP Power wants Y3. Y1+Y2+Y3 = X1 * 0.5

Z1 (Mummy every night got headache) + Z2 (Female colleague just started work and is 21 yrs old with 36C assets.). Assume Company always got overtime T+3

Solve for X, Y and Z

 

Where is the Z4? :huh:

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Tigerwoods

Tigerwoods

Turbocharged

You have to read the question carefully. Its not "4 fewer than 1/3", its 4 fewer then 1/3 of the remainder" (means 1/3 of 2/3 of total)-4 are red

 

Personally, I think the question can be better phase, & I do not like to have sentences that is confusing. In work, if someone write like this, I will tell him/her to amend the sentence.

NBzzz if adult read it also Liak BO Kio, P6 child how to understand ?

In fact most maths English questions are very badly phrased.

 

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Puteh83

Puteh83

1st Gear

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

 

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

 

u worried becos u r afriad that u can't solve if they ask u right? :D

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Wind30

Wind30

Turbocharged

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

 

yup that was my answer in page one. Basically the total number of ribbons can be 27,36,45 onwards.....multiple of nines. infinite solution. As I said, stupid question.

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The_Bear

The_Bear

Turbocharged
(edited)

Did i mention ah girl's home tutor is younger than me and quite a chio bu as well. ^_^

 

Maybe i ask for her to tutor me as well. [smash]

 

I think I need some close instructions too. How much she charges by the hour? ^_^

 

oh, NPNT... [smash]

Edited by Bavarian
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Thargor

Thargor

1st Gear

Very Simple lah

 

X = 1/3 of all Ribbons

 

Pink = X number of ribbons

Red = X - 4 ribbons

Yellow = X + 4 ribbons

 

Because Pink = 1/3

So..

 

X + (X+4) - (X-4) = 3X

2X + 8 = 3X

X = 8

 

So Pink is 8 ribbon. Together ribbon is 24. :D

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Hiphiphoray

Hiphiphoray

6th Gear

STILL WRONG!!!

 

Must draw box box one. Cannot use algebra rah.

 

Zero Mark for you. [laugh]

 

Very Simple lah

 

X = 1/3 of all Ribbons

 

Pink = X number of ribbons

Red = X - 4 ribbons

Yellow = X + 4 ribbons

 

Because Pink = 1/3

So..

 

X + (X+4) - (X-4) = 3X

2X + 8 = 3X

X = 8

 

So Pink is 8 ribbon. Together ribbon is 24. :D

 

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