Q&A - P3 Math

[jwxh]

pls help to solve this problem. i need working and explanation plse.

A packet of beads was shared equally among 28 girls.
8 girls decided to give up their beads to the rest.
As a result, the rest of the girls recd 2 more beads each.
How many beads were there in the packet at first? Ans: 140

[ponyo]

jwxh:

pls help to solve this problem. i need working and explanation plse.

A packet of beads was shared equally among 28 girls.
8 girls decided to give up their beads to the rest.
As a result, the rest of the girls recd 2 more beads each.
How many beads were there in the packet at first? Ans: 140

As a result of the 8 girls giving up their beads, the remaining 20 (ie 28-8) girls received 2 more beads each.
So the 20 girls received 20*2=40 extra beads in total
The 40 beads came from the 8 girls, so it means originally the girls each had 40/8=5

This means that the 28 girls have 28*5 = 140 beads altogether

[Sun_2010]

jwxh:

pls help to solve this problem. i need working and explanation plse.

haha, you are thinking too much A packet of beads was shared equally among 28 girls.
8 girls decided to give up their beads to the rest.
As a result, the rest of the girls recd 2 more beads each.
How many beads were there in the packet at first? Ans: 140

http://i50.tinypic.com/6xrs4y.jpg\">

[jwxh]

tks, everyone

[jessielu]

Need some help to solve the below qn:


Mr Tan bakes some curry puffs to give to his neighbours. If he gives 5 curry puffs to each neighbour, he will have 3 extra. If he gives 7 curry puffs to each neighbour, he will need 13 more. How many curry puffs did Mr Tan bake?

[tianzhu]

jessielu:

Need some help to solve the below qn:


Mr Tan bakes some curry puffs to give to his neighbours. If he gives 5 curry puffs to each neighbour, he will have 3 extra. If he gives 7 curry puffs to each neighbour, he will need 13 more. How many curry puffs did Mr Tan bake?

Hi

There are a few ways to do this question.

One possible way is to look from this angle.

To give 2 (7-5) more curry puffs to each neighbor, Mr Tan needs 16 (3 + 13) more curry puffs.

Number of neighbours ------- 16/2 ------- 8

Number of curry puffs baked by Mr Tan ------- 8*5 + 3 ------- 43

or 8*7 - 13 ------ 43

Best wishes

[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?

[qms]

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?

BigD,

At P3 level, this is the only method to solve the question. The other method is taught at...university level.

The answer is not unique if you increase the number of sweets. If you were to continue the list, you would realise that 29 could be an answer, too.

[BigDevil]

qms:

BigD,

At P3 level, this is the only method to solve the question. The other method is taught at...university level.

Thanks, qms. So DD just have to learn this method of solving this kind of problem.
[quote]The answer is not unique if you increase the number of sweets. If you were to continue the list, you would realise that 29 could be an answer, too.[/quote]I realise that, and had told DD that every increase of 15 (common multiple of 3 and 5) is a possible answer to the question. That's why the question had to state that Alicia has fewer than 20 sweets to make the answer unique.

[qms]

BigDevil:

Thanks, qms. So DD just have to learn this method of solving this kind of problem.

In a way, if such question appears in SA2, the number (as in the total number of sweets) will not be big. Hence, it won't take too long before you arrive at the answer.

If you review your list again, you will notice that the number of bags is not constant. If you put 3 sweets in a bag, there will be 4 bags. If you put 5 sweets in a bag, there will be 3 bags. Since the numbers of bags are different in the two scenarios, the standard formula cannot be applied.