Q&A - P3 Math

[Sun_2010]

cindyll:

Hi Parents


Appreciate your help on P3B text book question.

Total length of ribbon A & B is 30cm. Mrs Sim cut 3cm from ribbon A. In the end, ribbon B is twice as long as ribbon A. What is the length of ribbon A?

I got 2 possible answers, 9 and 13. May I know which one is correct?

Thank you very much for assisting.

initial lenght of A cannot be 13 cm.

9 is the only correct answer

[Funz]

cindyll:

Funz:

[quote=\"cindyll\"]Hi Parents


Appreciate your help on P3B text book question.

Total length of ribbon A & B is 30cm. Mrs Sim cut 3cm from ribbon A. In the end, ribbon B is twice as long as ribbon A. What is the length of ribbon A?

I got 2 possible answers, 9 and 13. May I know which one is correct?

Thank you very much for assisting.

I got 9cm. Cannot be 13cm. If 13cm the total length for the ribbons will be more than 30.

Thanks Funz. Will have to go back to school this Friday to confirm with the teacher.[/quote]
Ok now I see where the confusion is. If the question is interpreted as after 3cm is cut from A the total length is 30, and that the question is asking for the length of A at the beginning, the answer would be 13cm.

[Nebbermind]

Shouldn't the answer be 9cm? Mrs Sim already cut A (the qn did not say 'If Mrs Sim...').


BTW, the length before cutting is 12cm, not 13cm. 12 cm + 18cm = 30cm.

[cindyll]

Nebbermind:

Shouldn't the answer be 9cm? Mrs Sim already cut A (the qn did not say 'If Mrs Sim...').


BTW, the length before cutting is 12cm, not 13cm. 12 cm + 18cm = 30cm.

Thanks Nebbermind. Guess the answer now is either 9 or 12. Will have to ask the math teacher this Friday.

Will let you guys know the correct answer.

[qms]

cindyll:

Total length of ribbon A & B is 30cm. Mrs Sim cut 3cm from ribbon A. In the end, ribbon B is twice as long as ribbon A. What is the length of ribbon A?


I got 2 possible answers, 9 and 13. May I know which one is correct?

Thank you very much for assisting.

Funz:

Ok now I see where the confusion is. If the question is interpreted as after 3cm is cut from A the total length is 30, and that the question is asking for the length of A at the beginning, the answer would be 13cm.

The question started by stating that the length of the ribbon A & B is 30 cm. Thereafter, Mrs Sim cut out 3 cm. Hence, it should not be the case that 30 cm refers to the length after Mrs Sim cut out 3 cm.

[lotto]

Nebbermind:

Shouldn't the answer be 9cm? Mrs Sim already cut A (the qn did not say 'If Mrs Sim...').


BTW, the length before cutting is 12cm, not 13cm. 12 cm + 18cm = 30cm.

Any different whether u use IF or not?
Maybe the question is rephrased and some details are gone
so conclusion A at first is 12 cm and in the end is 9 cm.
Anyway why didn't anybody do the working here? haha

[Funz]

qms:

cindyll:

Total length of ribbon A & B is 30cm. Mrs Sim cut 3cm from ribbon A. In the end, ribbon B is twice as long as ribbon A. What is the length of ribbon A?


I got 2 possible answers, 9 and 13. May I know which one is correct?

Thank you very much for assisting.

Funz:

Ok now I see where the confusion is. If the question is interpreted as after 3cm is cut from A the total length is 30, and that the question is asking for the length of A at the beginning, the answer would be 13cm.

The question started by stating that the length of the ribbon A & B is 30 cm. Thereafter, Mrs Sim cut out 3 cm. Hence, it should not be the case that 30 cm refers to the length after Mrs Sim cut out 3 cm.

Hehe, yah, I was wondering how she got 13cm.

My answer is still 9cm. Not 12cm either since the question did not ask for the length of A at the beginning.

[Nebbermind]

It would be clearer is the sentence had started with

"Length of A and B WAS…"

Followed by,
"Mrs Sim cut…"

If they want to know the length before cutting, they should ask,
"What WAS the length of A…"

If they want to know the new length,
"What Is the length…"

Case 2

"If Mrs Sim cut…" but in actual fact, she didn’t cut. So there is ONLY one length, ie, the original length.

That’s just my interpretation. The teacher may not agree.

PS: OK I got what the issue is…original total = 30 or 33cm and so 13cm is possible too…Yes, must ask the teacher the intent of the qn.

[lotto]

Nebbermind:

It would be clearer is the sentence had started with

\"Length of A and B WAS...\"

Followed by,
\"Mrs Sim cut...\"

If they want to know the length before cutting, they should ask,
\"What WAS the length of A...\"

If they want to know the new length,
\"What Is the length...\"

Case 2

\"If Mrs Sim cut...\" but in actual fact, she didn't cut. So there is ONLY one length, ie, the original length.

That's just my interpretation. The teacher may not agree.

PS: OK I got what the issue is...original total = 30 or 33cm and so 13cm is possible too...Yes, must ask the teacher the intent of the qn.

I see. If the 30 cm is after cut then the answer is 13 cm.

Anyway your interpretation is correct! Agree wit it!

That's why I said the problem is the question. It was too ambiguous. The original question might be different from what written here.

[Nebbermind]

Some school exam setters just do not realise how important grammar is when it come to even simple P3 qns.