Q&A - PSLE Math

[tianzhu]

Belle2011:

Dear tian-zhu,

Thank very much for sharing another way of presenting the solution.
I was stuck with \"After B took 5/6 of the remaining tin of cookies...\".
So 5/6 * 1/6 = 5/36.
I am thinking \"my gosh! 5/36, how to draw the model...\".
Anyway, I am trying to reduce the number of 5 mark problem sums which I can't solve to as low as possible and you have been helping me all along.
Once again, thanks a lot.
Cheers,
Belle.

Hi

You're welcome.

Best wishes

[tianzhu]

LaiHeng:

have a question to ask ;

Jane bought 12 roses and 9 lilies for her mother. Each rose cost $2.50 less than each lily. If the total cost of the lilies was $0.50 more than the total cost of the roses, how much did Jane spend on the flowers altogther?

Hi

A quick one

9*2.5 -------22.5

12 units + 0.5 --------- 9 units + 22.5 (total cost of the lilies was $0.50 more than the total cost of the roses)

3 units -------- 22
21 units -------154

(154+22.5) -------176.5

Jane spent $176.50 on the flowers.

Best wishes

[small]

ADoc:

LaiHeng:

[quote=\"small\"]

Hi,

HTH..


The key step is to calculate Joe's percentage. Given that Amos's salary is 20% less than Joe's.

80% of Joe = 120% of Steve
100% of Joe = 150% of Steve

Steve = 100% (10 Units)
Amos = 120% (12 Units)
Joe = 150% (15 Units)

37 Units = 2220
1 Unit = 60
12 Unit = 720

or
370% = 2220
1% = 6
120% = 720.

to anyone,
can someone enlighten how 100% of Joe = 150% of Amos?
I can't catch any clues on how to derive it.

Hi, I believe there was a typo error in the answer above.
It should be 100% of Joe = 150% of Steve instead of Amos.

Hope this clarifies.
cheers
ADoc[/quote]

Hi LaiHeng,

My apologies for the typo error. :stupid: It should be 80% of Joe = 120% of Steve.



Many thanks to Adoc for pointing out my error. :celebrate: :celebrate:

[small]

is_me_lblue:

is_me_lblue:

Hi,


I am stuck again.

Amos'salary is 20% more than Steve's but 20% less than Joe's. If their total salary is $2220,find Amos's salary.

I always get the answer of 740 but answer given is 720.

Thank you

Small,

Thank you, I not so good in math so have to learn together with my son.

Hi,

Plese refer my revised solution. Apologies for the typo error in my ealier post

http://farm6.static.flickr.com/5138/5488155395_fe1c7f694a_b.jpg\">

[spunky]

Firsly, I think do you have a issue with deciding who is the 100%? That is usually on eof the common problem.Maybe you can send me ur solution then I can help u diagnose why u arrive at $740


Secondly, remember that Ratio, percentage and fraction can be used to solve a problem sum despite the question being a % question.

Solution (Ratio method) which is what I would usually use for this type of questions.


A : S
120 : 100
6 : 5
x 2 x 2
J : A
100 : 80
5 : 4
x 3 x 3

J : A : S
15 : 12 : 10

37 units --> 2220
1 unit --> 2220 ÷ 37
--> 60
12 units --> 60 x 12
--> $720

small:

is_me_lblue:

[quote=\"is_me_lblue\"]Hi,

I am stuck again.

Amos'salary is 20% more than Steve's but 20% less than Joe's. If their total salary is $2220,find Amos's salary.

I always get the answer of 740 but answer given is 720.

Thank you

Small,

Thank you, I not so good in math so have to learn together with my son.

Hi,

Plese refer my revised solution. Apologies for the typo error in my ealier post

http://farm6.static.flickr.com/5138/5488155395_fe1c7f694a_b.jpg\">

8)[/quote]

[ozora]

tianzhu:

LaiHeng:

have a question to ask ;

Jane bought 12 roses and 9 lilies for her mother. Each rose cost $2.50 less than each lily. If the total cost of the lilies was $0.50 more than the total cost of the roses, how much did Jane spend on the flowers altogther?

Hi

A quick one

9*2.5 -------22.5

12 units + 0.5 --------- 9 units + 22.5 (total cost of the lilies was $0.50 more than the total cost of the roses)

3 units -------- 22
21 units -------154

(154+22.5) -------176.5

Jane spent $176.50 on the flowers.

Best wishes

thanks .. is really clear explanation

[ozora]

ADoc:

LaiHeng:

[quote=\"small\"]

Hi,

HTH..


The key step is to calculate Joe's percentage. Given that Amos's salary is 20% less than Joe's.

80% of Joe = 120% of Amos
100% of Joe = 150% of Amos

Steve = 100% (10 Units)
Amos = 120% (12 Units)
Joe = 150% (15 Units)

37 Units = 2220
1 Unit = 60
12 Unit = 720

or
370% = 2220
1% = 6
120% = 720.

to anyone,
can someone enlighten how 100% of Joe = 150% of Amos?
I can't catch any clues on how to derive it.

Hi, I believe there was a typo error in the answer above.
It should be 100% of Joe = 150% of Steve instead of Amos.

Hope this clarifies.
cheers
ADoc[/quote]thanks to everyone and Adoc. It cleared my doubts.

[ozora]

another 2 new questions:

1. Every Child was accompanied by either 1 or 2 parents to a concert. If the ratio of the number of children to the number of parents is 12:17, what fraction of the children came 2 parents?

2. A bag contains 200 blue balls and 450 yellow balls. A tin contains 850 blue and 340 yellow balls. After some blue and yellow balls are moved from the tin to the bag, the percentage of the blue balls in the bag becomes 50% and the blue balls in the tin becomes 70%.
a)How many blue balls are moved from the tin to the bag?
b)How many yellow balls are moved from the tin to the bag?


thanks

[tianzhu]

Hi LaiHeng


Good Morning.

Here's the solution to Q1.

Hope this helps.

Best wishes

http://farm6.static.flickr.com/5095/5490097769_cb20f73bac_b.jpg\">

[tianzhu]

LaiHeng:

thanks .. is really clear explanation

Hi

You're welcome.

Best wishes