Q&A - PSLE Math

[MathIzzzFun]

peggy:

MathIzzzFun:

[quote=\"superworried mum\"]Hi, can someone pls help in this question


There are more pens in box A than Box B. 30% of the pens in box A is 60 more than 40%
of the pens in Box B. If 5% of the pens in Box A is transferred into Box B, there will be 300 more pens in Box A than Box B.

a) How many pens are there in Box B?
b) How many percent less pens are there in Box B than Box A?

Thanks

Hi

(3/10 A = 6/20 A, 2/5 B = 6/15 B)
B --> 15u
A --> 20u+ 200

5% of A --> 1u + 10
After transfer:
B --> 16u + 10
A --> 19u + 190
A has 300 more than B
So, 19u + 190 = 16u + 10 + 300
1u --> 40

...I think you can complete the rest from here

cheers.

Hi MathIzzzfun,

Why is it A ---- 20U + 200 ? Understood for the 20U but not the 200.

Thanks.[/quote]B--> 15u, so 40% = 6u
30% of A is 60 more than 40% of B,
So, 30% of A = 6u + 60
10% of A = 2u + 20
1005 of A = 20u + 200

cheers.

[speedmaths.012624com]

superworried mum:

Hi, can someone pls help in this question


There are more pens in A than B.
30% of the pens in A is 60 more than 40% of the pens in B.
If 5% of the pens in A is transferred into B, there will be 300 more pens in A than B.

a) How many pens are there in B?
b) How many percent less pens are there in B than A?

Thanks

Hi,

Lets try to solve this using the Advanced Model Method (or Bags and Boxes).
(Pupils used to the simple Model Method may picture / think of a Box as a Rectangle, and a Bag as a Circle)

Let there be 100 Bags (of pens) in A.
Let there be 100 Boxes (of pens) in B.

(30% of the pens in A is 60 more than 40% of the pens in B.)
30 bags = 40 Boxes + 60

(If 5% of the pens in A is transferred into B, there will be 300 more pens in A than B.)
95 bags = 100 Boxes + 5 Bags + 300
90 bags = 100 Boxes + 300

30 bags = 40 Boxes + 60
(x 3)
90 bags = 120 Boxes + 180

90 bags = 100 Boxes + 300

90 bags = 120 Boxes + 180 = 100 Boxes + 300
120 Boxes + 180 = 100 Boxes + 300
20 Boxes + 180 = 300
20 Boxes = 120
10 Boxes = 60

B = 100 Boxes = ??

90 bags = 100 Boxes + 300
90 bags = ??
10 bags = ??

A = 100 bags = ??

Can you solve from here?

Hope this helps.

The Advanced Model Method (or Bags and Boxes Method) may be found in the book Raffles Maths Tricks - Volume 1; which has been available in local book stores since 2006.

We will demonstrate this method at our Parents’ Workshop.
Please see thread on the Happenings forum.

Cheers


speedmaths.com

.

[peggy]

Please help with this CA1 from Ai Tong.


In a survey, some pupils were asked if they preferred volleyball or table tennis. 13/20 of the pupils chose volleyball, 75% of the pupils chose table tennis and 5% of the pupils did not choose any of the two sports. Given that 90 pupils chose both volleyball and table tennis, how many pupils took part in the survey ?

thank you !

[tianzhu]

peggy:

Please help with this CA1 from Ai Tong.


In a survey, some pupils were asked if they preferred volleyball or table tennis. 13/20 of the pupils chose volleyball, 75% of the pupils chose table tennis and 5% of the pupils did not choose any of the two sports. Given that 90 pupils chose both volleyball and table tennis, how many pupils took part in the survey ?

thank you !

Hi

13/20 ------ 65% ------- volleyball
75% ------- table tennis

100% - 5% ------- 95% -------- pupils who chose any of the two sports.

140% - 95% ------ 45% -------- pupils who chose both volleyball and table tennis

45% ------ 90

100% ------- 200

Best wishes

[superksmum]

Pls help with this question:


A lion and zebra were 138m apart. Upon seeing the lion, the zebra ran away from the lion at average speed of 16m/s. The lion observed the zebra for 1 minute before giving chase at an average speed of 25m/s. From the time it started giving chase, how long did the lion take to catch up with the zebra?

Thank you.

[peggy]

tianzhu:

peggy:

Please help with this CA1 from Ai Tong.


In a survey, some pupils were asked if they preferred volleyball or table tennis. 13/20 of the pupils chose volleyball, 75% of the pupils chose table tennis and 5% of the pupils did not choose any of the two sports. Given that 90 pupils chose both volleyball and table tennis, how many pupils took part in the survey ?

thank you !

Hi

13/20 ------ 65% ------- volleyball
75% ------- table tennis

100% - 5% ------- 95% -------- pupils who chose any of the two sports.

140% - 95% ------ 45% -------- pupils who chose both volleyball and table tennis

45% ------ 90

100% ------- 200

Best wishes

Thanks, Tianzhu.

But any possibility of a mode. Think my DS can digest better with it.

Sorry to trouble you.

[tianzhu]

peggy:

Thanks, Tianzhu.

But any possibility of a mode. Think my DS can digest better with it.

Sorry to trouble you.

Hi

Hope this helps.

Best wishes.

http://farm8.staticflickr.com/7243/6966119100_e47f2d8176_z.jpg\">

[tianzhu]

superksmum:

Pls help with this question:


A lion and zebra were 138m apart. Upon seeing the lion, the zebra ran away from the lion at average speed of 16m/s. The lion observed the zebra for 1 minute before giving chase at an average speed of 25m/s. From the time it started giving chase, how long did the lion take to catch up with the zebra?

Thank you.

Hi

As in any questions on Speed, start with a simple diagram.

In 1 min (60 seconds) , the zebra covered (16*60) or 960m.

138 + 960 ----- 1098

25 – 16 ----- 9

1098/9 ------ 122

Time for lion to catch up with zebra ------- 122 seconds.

Best wishes

[superksmum]

Hi Tianzhu,


Thank you so much for the explanation. My DD is able to understand the concept.
Just wonder how to insert a picture or diagram as there is also another question on circle that we are very confused.

Thank you

[tianzhu]

superksmum:

Hi Tianzhu,


Thank you so much for the explanation. My DD is able to understand the concept.
Just wonder how to insert a picture or diagram as there is also another question on circle that we are very confused.

Thank you

Hi

You’re welcome.

You may insert image by following these steps.

1) Do a print screen of the portion you want to upload.

2) Edit using Paint. Cut out the portion of the question you want to upload.

3) Save file in pictures

4) Go to Flickr (Free sign up as member) or other storage sites. Upload file. Select biggest/medium size. Right click to copy URL of image.

5) Coming back to Kiasuparents forum, click insert image button.

Alternatively, if the question is from past years papers, you may just provide a link to the test paper (name of school, year). Please indicate the question number and page number of the paper.

http://www.orlesson.org/orp/MathExam.html

Best wishes