Q&A - PSLE Math

[CoffeeCat]

Nope i think that an if scenario means it will take place unless the question is somehow worded to meant that the if scenario is purely hypothetical and never happen. Unless of course I am too out of touch with psle problem sums.

Then again it will be good if there are samples of such actual questions. However I notice usually the question is "if blah blah blah, find blah.", which is not too ambiguous.

[sexymama]

To those 'Wonderful Gurus',

Tks for the superb solutions.... :lol:

[firebird]

Dear Dharma


Thank you very much for your working and answer.

With best regards
firebird

[firebird]

Dear Ksi


Thank you for your working and answer.

With best regards
firebird

[liketoeat]

Tang:

liketoeat:

To all the gurus,


I need clarification for the following question:

5/13 of a rectangular tank, 64 cm long, 30 cm wide and 65 cm high, was filled with water.
a) If 14.4 litre of water is poured into the tank, what would be the height of the water in the tank now?
b) Water is then poured into the tank at the rate of 480 cubic cm per minute. How long would it take for the tank to be completely filled? express your answer in h.

Do we take the height found in (a) to get the answer for (b) or do we treat (a) and (b) separately?

Thank you.

Hello,

a) should have been written as:

a) When 14.4 litre of water was poured into the tank, what would be the height of the water in the tank then?

Use new height for part (b)

or

a) If 14.4 litre of water had been poured into the tank, what would be the height of the water in the tank?

Use old height for part (b)

Hi Tang,

Your reply and Dharma's reply aren't the same so I'm still confuse.

When I first started doing the question, I treated the 2 parts separately because of the word 'if'. Then, when I read Dharma's solution, I realised that he treated the 2 parts one after the other because of the word 'then'.

Perhaps 'if' should not be used in this question otherwise there'll be 2 solutions....

Thank you for your response.

[Muffins]

liketoeat:

Tang:

[quote=\"liketoeat\"]To all the gurus,


I need clarification for the following question:

5/13 of a rectangular tank, 64 cm long, 30 cm wide and 65 cm high, was filled with water.
a) If 14.4 litre of water is poured into the tank, what would be the height of the water in the tank now?
b) Water is then poured into the tank at the rate of 480 cubic cm per minute. How long would it take for the tank to be completely filled? express your answer in h.

Do we take the height found in (a) to get the answer for (b) or do we treat (a) and (b) separately?

Thank you.

Hello,

a) should have been written as:

a) When 14.4 litre of water was poured into the tank, what would be the height of the water in the tank then?

Use new height for part (b)

or

a) If 14.4 litre of water had been poured into the tank, what would be the height of the water in the tank?

Use old height for part (b)

Hi Tang,

Your reply and Dharma's reply aren't the same so I'm still confuse.

When I first started doing the question, I treated the 2 parts separately because of the word 'if'. Then, when I read Dharma's solution, I realised that he treated the 2 parts one after the other because of the word 'then'.

Perhaps 'if' should not be used in this question otherwise there'll be 2 solutions....

Thank you for your response.[/quote]Hi liketoeat,

Sorry to intrude, but I think Tang's method is the correct one, as the 14.4 litres were not actually put into the tank. I think the purpose of the \"then\" is to move it to another timeframe, as it does not want to confuse you about the \"if\". On the whole, I think that the question is quite ambiguous, but Tang's answer hinges more on my gut feeling that it is correct.

Maybe Tianzhu can be the tie-breaker? :idea:

[liketoeat]

Muffins:

liketoeat:

[quote=\"Tang\"]

Hello,

a) should have been written as:

a) When 14.4 litre of water was poured into the tank, what would be the height of the water in the tank then?

Use new height for part (b)

or

a) If 14.4 litre of water had been poured into the tank, what would be the height of the water in the tank?

Use old height for part (b)

Hi Tang,

Your reply and Dharma's reply aren't the same so I'm still confuse.

When I first started doing the question, I treated the 2 parts separately because of the word 'if'. Then, when I read Dharma's solution, I realised that he treated the 2 parts one after the other because of the word 'then'.

Perhaps 'if' should not be used in this question otherwise there'll be 2 solutions....

Thank you for your response.

Hi liketoeat,

Sorry to intrude, but I think Tang's method is the correct one, as the 14.4 litres were not actually put into the tank. I think the purpose of the \"then\" is to move it to another timeframe, as it does not want to confuse you about the \"if\". On the whole, I think that the question is quite ambiguous, but Tang's answer hinges more on my gut feeling that it is correct.

Maybe Tianzhu can be the tie-breaker? :idea:[/quote]Thank you Muffins. Let's hope others can enlighten us on this once and for all. Thanks again.

[Muffins]

liketoeat:

Muffins:

[quote=\"liketoeat\"]
Hi Tang,

Your reply and Dharma's reply aren't the same so I'm still confuse.

When I first started doing the question, I treated the 2 parts separately because of the word 'if'. Then, when I read Dharma's solution, I realised that he treated the 2 parts one after the other because of the word 'then'.

Perhaps 'if' should not be used in this question otherwise there'll be 2 solutions....

Thank you for your response.

Hi liketoeat,

Sorry to intrude, but I think Tang's method is the correct one, as the 14.4 litres were not actually put into the tank. I think the purpose of the \"then\" is to move it to another timeframe, as it does not want to confuse you about the \"if\". On the whole, I think that the question is quite ambiguous, but Tang's answer hinges more on my gut feeling that it is correct.

Maybe Tianzhu can be the tie-breaker? :idea:

Thank you Muffins. Let's hope others can enlighten us on this once and for all. Thanks again.[/quote]Anytime! (BTW, your moniker makes me hungry! :))

[firebird]

Dear Dharma


Good evening.

First I have to tell you that i sincerely appreciate your help.

I am unable to follow your working (posted on 23 June 2010 for my doubts) for Question 1 rasied by me. This question refers to Melvin, Tomas and Jack taking out coins from piggy bank.

My doubts are:
1) How many biggy banks are there.
2) Why 4/5 X 795 = 636
And then 795 - 636 = 159

What I worked out from the solution given by you as I was totally lost before was this:
Let Thomas be T, Melvin be M, Jack be J

Given T + J = 795
Given M + T = 5/13
Given J + M = 4/5

So J + T = 2 - 5/13 - 4/5 = 52/65
53u = 795
u = 15

Then J - M = (J+T) - (J+M) = 53/65 - 4/5
= 53/65 - 52/65
= 795 - 780(52x15)
= 15

What i am getting is 15.

I know i am wrong.

Please guide me. New or addtional method to derive a solution is most welcome.

Thank you.
Firebird

[Tang]

firebird:

Dear Dharma


Good evening.

First I have to tell you that i sincerely appreciate your help.

I am unable to follow your working (posted on 23 June 2010 for my doubts) for Question 1 rasied by me. This question refers to Melvin, Tomas and Jack taking out coins from piggy bank.

My doubts are:
1) How many biggy banks are there.
2) Why 4/5 X 795 = 636
And then 795 - 636 = 159

What I worked out from the solution given by you as I was totally lost before was this:
Let Thomas be T, Melvin be M, Jack be J

Given T + J = 795
Given M + T = 5/13
Given J + M = 4/5

So J + T = 2 - 5/13 - 4/5 = 52/65
53u = 795
u = 15

Then J - M = (J+T) - (J+M) = 53/65 - 4/5
= 53/65 - 52/65
= 795 - 780(52x15)
= 15

What i am getting is 15.

I know i am wrong.

Please guide me. New or addtional method to derive a solution is most welcome.

Thank you.
Firebird

Hello,

I hope I am fully awake.

\"Then J - M = (J+T) - (J+M) = 53/65 - 4/5\"

(J+T) - (J+M) = T - M [and not (J - M)].