Q&A - PSLE Math

[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)].

[firebird]

Dear Tang


Good morning.

You are correct. It shoud be T - M as per question.

I am very sorry for the typing error.

Thank you.
Firebird

[Dharma]

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

Hi firebird,

Your answer is correct. I'm sorry abt the careless mistake and thanks for pointing it out and now have amended the solution.

Q1)
Melvin & Thomas => 5/13
Jack & Melvin => 4/5
Jack & Thomas = > 2 – 5/13 – 4/5 = 53/65
53u = 795
1u = 15

Diff = 53u – 52u = 1u = 15 (Thomas took out Melvin 15 more coins than Melvin)

[firebird]

Dear Dharma


Good morning.

Many thanks for your answer.

Your help is very much appreciated.

With best regards
firebird

[Tang]

firebird:

1) Melvin, Thomas and Jack put some coins in a piggy bank. They wanted to donate some money to the charity, so Thomas and Jack took out 795 coins. Melvin and Thomas took out 5/13 of the coins from their piggy bank. Jack and Melvin took out 4/5 of the coins from their piggy bank. How many more coins did Thomas take than Melvin?

T + J --> 795 coins

M + T --> 5/13 = 25/65

M + J --> 4/5 = 52/65

2 M + T + J --> 25/65 + 52/65 = 77/65

1 M --> 77/65 - 65/65 = 12/65 (since M + T + J = 1 = 65/65)

2 M --> 12/65 x 2 = 24/65

T --> 25/65 - 12/65 = 13/65

T - M --> 13/65 - 12/65 = 1/65

T + J --> 77/65 - 24/65 = 53/65

53 u --> 795 coins

1 u --> 795/53 = 15 coins

Thomas took 15 more coins than Melvin.

[liketoeat]

[/quote]


Anytime! (BTW, your moniker makes me hungry! :))[/quote]


yours too, muffins, yumyum