Q&A - P3 Math

[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.

[qms]

Nebbermind:

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

For one moment, I thought I was in the Q&A - English thread. http://i826.photobucket.com/albums/zz186/willisnowell/smilies/smiley_wink.gif\">

[Sunflower03]

BigDevil:

Alicia has fewer than 20 sweets.

She puts the sweets into packets such that each packet will have the same number of sweets.
If she puts them into packets of 3, she will have 2 sweets left over.
If she puts them into packets of 5, she will be short of 1 sweet.
How many sweets does Alicia have?

I know this can be solved by listing...

n x 3 + 2: 5 8 11 14 17
n x 5 - 1: 4 9 14 19
Ans: 14 sweets

Are there any other methods?

Hi Big Devil,

May I know how you get 5 8 11 14 17 and 4 9 14 19?

I still can't get it right.

Kindly enlightening me.

Thanks!

[BigDevil]

The numbers are to satisfy the conditions stated in the question.


If she puts them into packets of 3, she will have 2 sweets left over.
The unknown here is the number of packets.
So if there is one packet, number of sweets will be (1 x 3) + 2 = 5
2 packets, (2 x 3) + 2 = 8
3 packets, (3 x 3) + 2 = 11
4 packets, (4 x 3) + 2 = 14
5 packets, (5 x 3) + 2 = 17
You can stop here since the question states that Alicia has fewer than 20 sweets.

Likewise, for the second part of the question: If she puts them into packets of 5, she will be short of 1 sweet.
You go through the same process again.
1 packet, (1 x 5) - 1 = 4
2 packets, (2 x 5) - 1 = 9
3 packets, (3 x 5) - 1 = 14
4 packets, (4 x 5) - 1 = 19

Since the number of sweets does not change, that same number must appear in both sets of working so as to satisfy both conditions, and that number is 14.

Clear now?

[dazzlego]

Sunflower03:

BigDevil:

Alicia has fewer than 20 sweets.

She puts the sweets into packets such that each packet will have the same number of sweets.
If she puts them into packets of 3, she will have 2 sweets left over.
If she puts them into packets of 5, she will be short of 1 sweet.
How many sweets does Alicia have?

I know this can be solved by listing...

n x 3 + 2: 5 8 11 14 17
n x 5 - 1: 4 9 14 19
Ans: 14 sweets

Are there any other methods?

Hi Big Devil,

May I know how you get 5 8 11 14 17 and 4 9 14 19?

I still can't get it right.

Kindly enlightening me.

Thanks!

Hi Sunflower03,
It is \"multiple of 3 (+ 2)\" and \"multiple of 5 (- 1)\"

Hi Big Devil,
Yes, there is another method. You can use this method if all the cases have the same remainder or have the same shortage.
In this question both cases have the same shortage since \"If she puts them into packets of 3, she will have 2 sweets left over\" has the same meaning as \"if she put them into packets of 3, she will be short of 1\"
Then, find a common multiple of 3 and 5 first and after that subtract 1 (shortage) from it

Cheers :celebrate:

[BigDevil]

:shock: Amazing!


It didn't even occur to me that excess of 2 is equivalent as saying shortage of 1! Certainly makes the solution a lot easier!

Thanks!!

[Sunflower03]

dazzlego:

Sunflower03:

[quote=\"BigDevil\"]Alicia has fewer than 20 sweets.

She puts the sweets into packets such that each packet will have the same number of sweets.
If she puts them into packets of 3, she will have 2 sweets left over.
If she puts them into packets of 5, she will be short of 1 sweet.
How many sweets does Alicia have?

I know this can be solved by listing...

n x 3 + 2: 5 8 11 14 17
n x 5 - 1: 4 9 14 19
Ans: 14 sweets

Are there any other methods?

Hi Big Devil,

May I know how you get 5 8 11 14 17 and 4 9 14 19?

I still can't get it right.

Kindly enlightening me.

Thanks!

Hi Sunflower03,
It is \"multiple of 3 (+ 2)\" and \"multiple of 5 (- 1)\"

Hi Big Devil,
Yes, there is another method. You can use this method if all the cases have the same remainder or have the same shortage.
In this question both cases have the same shortage since \"If she puts them into packets of 3, she will have 2 sweets left over\" has the same meaning as \"if she put them into packets of 3, she will be short of 1\"
Then, find a common multiple of 3 and 5 first and after that subtract 1 (shortage) from it

Cheers :celebrate:[/quote]

Thanks Ladies for your explanation. Learn another thing today.

[Sun_2010]

Sunflower03 - BigD is a gentleman


Dazzlego - like your method - really dazzling. Never tot of taking it to the next step and seeing the excess as shortage or the otherway around. I like!