Q&A - PSLE Math

[2DMommy]

Please help with this question :


After a maths quiz, Mr Li gave the 3 prize winners a box of pencils to share. The 1st winner received 2/3 of the pencils plus 1/3 of a pencil. The 2nd winner received 2/3 of the remainder plus 1/3 of a pencil. The 3rd winner received 2/3 of the new remainder plus 1/3 of a pencil, but there were no pencils left after this. How many pencils were there in all ?

thanks !

[MathIzzzFun]

mathnoobs:

MathIzzzFun:

[quote=\"Chan09\"]I do need help as I can solve using algebra but even looking at models this is tough:

a group of friends play tennis. each of them play with everyone else. Ann played with 4 times as many girls as boys. Bob played with 5 times as many girls as boys.
a) how many people were there altogether? ans: 31 people
b) were there more boys than girls and how many more? ans: 19 more girls than boys

Hi

Ann played with 4 times as many girls as boys, so
Girls : Boys --> 4u +1 : 1u,
total 5u + 1 people and there were 3u + 1 more girls

Bob played with 5 times as many girls as boys,
Girls : Boys --> 4u + 1 : 1u -1 = 5 : 1

cross multiply or equalize --> 4u + 1 = 5u -5
1u --> 6
5u + 1 = 31
3u+1 --> 19

There were 31 people and there were 19 more girls than boys.

cheers.

I'm afraid I don't get this:

Bob played with 5 times as many girls as boys,
Girls : Boys --> 4u + 1 : 1u -1 = 5 : 1

why is Boys = 1u-1 ? and Girls = 4u+1 ? is that from the previous statement ?[/quote]Hi

Ann played with 4 times as many girls as boys, so if she played with 1 unit of boys, she played with 4 units of girls. So, total number of girls = 4 units + 1 (Ann)

So, Bob will play with 1 unit - 1 (Bob) of boys and 4 units + 1 of girls.

cheers.

[anneshirleygilbert]

Hi MathIzzzFun,


Charlie had $490 more than Eugene. Charlie spent 1/7 of his money, Eugene spent 1/5 of his money. If Eugene spent $20 less than Charlie, find the total amount of money the children had in the end.


Eugene’s money –> 5 units
Eugene spent –> 1 unit
Charlie spent –> 1 unit + 20
Charlie’s money –> 7 x (1 unit + 20) = 7 units + 140
So, 7 units + 140 = 5 units + 490
1 unit –> 175
…you should be able to complete the solution from here

I’m a little confused. Should what Charlie spent have been 1u + 70?
seeing he spent (1/7 of 7 units and 1/7 of $490)?
We did this question using simultaneous equations and our answers are $1170 for Charlie and $700 for Eugene. Are our answers correct?

TIA

[small]

Hi anneshirleygilbert,


Your answer is correct.

[MathIzzzFun]

anneshirleygilbert:

Hi MathIzzzFun,


Charlie had $490 more than Eugene. Charlie spent 1/7 of his money, Eugene spent 1/5 of his money. If Eugene spent $20 less than Charlie, find the total amount of money the children had in the end.


Eugene's money --> 5 units
Eugene spent --> 1 unit
Charlie spent --> 1 unit + 20
Charlie's money --> 7 x (1 unit + 20) = 7 units + 140
So, 7 units + 140 = 5 units + 490
1 unit --> 175
...you should be able to complete the solution from here

I'm a little confused. Should what Charlie spent have been 1u + 70?
seeing he spent (1/7 of 7 units and 1/7 of $490)?
We did this question using simultaneous equations and our answers are $1170 for Charlie and $700 for Eugene. Are our answers correct?

TIA

Hi

yes, your answers are right. I started the solution from the end stage. You could start from the front of the question ie
Charlie --> 7u + 490,
Charlie spent --> 1u + 70,
Eugene spent --> 1u + 50, so
Eugene's money --> 5u + 250 = 7u
1u --> 125

cheers.

[anneshirleygilbert]

Thanks, MathIzzzFun. I see what you mean.... your units are based on Eugene's. Clear as crystal now. Thanks a bunch.


Thanks too, small. You go by the name 'small'.... I think you should change it to \"Big Hearted\"!!! Thanks a lot, too!.

[hazelwong]

Dear All,

Just want to clarify:
Are we allowed to use simultaneous equations in PSLE?
(cos the kids have not been taught this in pri school)
Although I know MOE stated that "In the marking of PSLE Mathematics, all mathematically correct solutions are acceptable and there is no loss of marks if a correct algebraic method is used. ", but I don’t know if the markers will cut points (or even follow MOE’s statement at all)

anyone’s kids used this and scored well for PSLE?
TIA

[anneshirleygilbert]

I should think solving problem sums by simultaneous equations is acceptable because my daughter’s math teacher in school uses it. Besides, some of my neighbours’ kids in P4 are using this method to solve their problem sums… and they’re pretty good at it! As far as I can remember, I only learnt SE in the upper grades, definitely not Grade 4 or 6!


But, I guess, kids these days are smarter!

[tianzhu]

2DMommy:

Please help with this question :


After a maths quiz, Mr Li gave the 3 prize winners a box of pencils to share. The 1st winner received 2/3 of the pencils plus 1/3 of a pencil. The 2nd winner received 2/3 of the remainder plus 1/3 of a pencil. The 3rd winner received 2/3 of the new remainder plus 1/3 of a pencil, but there were no pencils left after this. How many pencils were there in all ?

thanks !

Hi

Your question is quite similar to this question which was posted earlier.

Use the same way and try it out first.The answer is 13.

Best wishes

http://farm5.staticflickr.com/4019/4713599224_8f586290c0_z.jpg\">

[MathAche]

Nanyang P6 2011 CA1

Q16) Sushila went shopping. She spent $588 on 2 dresses, 3 skirts and 2 pairs of sunglasses. The total amount spent on the dresses was 0.4 of the total amount spent on the skirts and sunglasses. The total amount spent on the sunglasses was 1/3 of the total amount spent on dresses and skirts.
(a) how much did she spend on the 2 pairs of sunglasses?
(b) what was the cost of the third skirt if the average cost of the other 2 skirts was $88?

Looking for a model to help explain to my kid.