Q&A - PSLE Math

[angela]

Can anyone help in this question ( Raffles Girls 2009 SA1)?


Container A contains 250 red marbles and 200 blue marbles.
Container B contains 600 red marbles and 150 blue marbles.
How many red and blue marbles must be moved from Container A to Container B such that 25% of the marbles in Container A are red and 75% of the marbles in Container B are red?

Thanks

[tianzhu]

Hi

Hope this helps.
http://farm5.static.flickr.com/4122/4778205021_8f7608186f_b.jpg\">
Best wishes.

[Brenda10]

Hi, the quesiton is NY 2009 CA2 Q18. Please help to confim is the following steps by dd acceptable.


Q: Kailing and Jim had a total of $63. Kailing gave 0.3 of her share to Jim. Jim then gave 1/3 of the total amount of money he had to his brother. In the end, all the three children had the same amount of money. How muh money did Kailing have at first?
(Given answer is $36)

DD said at the end each of them had 2 units (ref from Jim), total would be 6 units


K - uu
J - uu
B- uu

Then trasnfer 2u from B back to J, it would become 5 units
(B's 2 u= 1u from J's previosuly), then become 5 units

K - uu
J- uuu

Since K and J share $63, then the following would be the working:

63 / 5u = 12.6
12.6 x 2u = 25.2
25.2/7 x 10 = 36

Answer: $36

The answer is correct but is the way of working acceptable? :?

Kindly advise. Thanks

[tianzhu]

Brenda10:

Then trasnfer 2u from B back to J, it would become 5 units
(B's 2 u= 1u from J's previosuly), then become 5 units

Hi Brenda10

Yes, your girl has found a neat way to tackle this question.I take it that she has done it using Model Drawing with 1u representing a box.

After giving 1 unit to his brother, Jim had 2 units in the end.
Perhaps, there are some typo errors here. It should read as then transfer 1u from B(Brother)back to J(Jim).

Best wishes

[Brenda10]

tianzhu:

Brenda10:

Then trasnfer 2u from B back to J, it would become 5 units
(B's 2 u= 1u from J's previosuly), then become 5 units

Hi Brenda10

Yes, your girl has found a neat way to tackle this question.I take it that she has done it using Model Drawing with 1u representing a box.

After giving 1 unit to his brother, Jim had 2 units in the end.
Perhaps, there are some typo errors here. It should read as then transfer 1u from B(Brother)back to J(Jim).

Best wishes

Hi Tianzhu

Yes you 're right. She told me to amend but may be I could not understand.

She did draw a model but I don't know how to present it. :oops:

Thank you very much for confirm her working as earlier I did not feel comfortable of her working.

Wish you a nice day.

[Maths Monster]

angela:

Can anyone help in this question ( Raffles Girls 2009 SA1)?


Container A contains 250 red marbles and 200 blue marbles.
Container B contains 600 red marbles and 150 blue marbles.
How many red and blue marbles must be moved from Container A to Container B such that 25% of the marbles in Container A are red and 75% of the marbles in Container B are red?

Thanks

Before:
Red in A = 250
Blue in A = 200
Total in A = 450

Red in B = 600
Blue in B = 150
Total in B = 750

After:
25% of the marbles in Container A are red
Red in A = u
Blue in A = 3u

Red in B = 250 + 600 - u = 850 - u (No change in total Red)
Blue in B = 200+ 150 - 3u = 350 - 3u (No change in total Blue)

Since 75% of the marbles in Container B are red, we can write:
(350 - 3u) x 3 = (850 - u)
1050 - 9u = 850 - u
8u = 200
u = 25

Therefore, after:
Red in A = 25
Blue in A = 75
Total in A = 100

Red in B = 850 - u = 825
Blue in B = 350 - 3u = 275
Total in B = 1100

Therefore:
Red move from A to B = 250 - 25 = 225
Blue moved from A to B = 200 - 75 = 125

Check:
After:
Red in A = 25
Blue in A = 75
Total = 100
Red % = 25/100 x 100% = 25%
=> 25% of the marbles in Container A are red

Red in B = 825
Blue in B = 275
Total in B = 1100
Red % = 825/110 x 100% = 75%
=> 75% of the marbles in Container B are red

[tianzhu]

Brenda10:

She did draw a model but I don't know how to present it. :oops:

Hi Brenda10.

You're welcome.

You may insert images by following the following 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 KSP forum, click image Img button.

Best wishes

[abc_parent]

Thanks to tianzhu & Maths Monster!!

[tianzhu]

abc_parent:

Thanks to tianzhu & Maths Monster!!

Hi

You're welcome.

Best wishes

[kitty2]

Please kindly help with these questions, :thankyou:


1)Minli has 32 English & Chinese books.4/5 of the English books & 3/4 of the chinese books are fiction books.She has a total of 25 fiction books.How many english fiction books are there?

2)Mr Miki had some track shoes in his shop.3/7 of them were Brand x,1/4 of the remainder were brand Y and the rest were brand Z


Types of shoes Amt earn/pair

Brand x $8
Brand Y $6
Brand Z $10

The table shows the amt he earn per pair of shoes.The number of brand X shoes sold to the number of Brand Y shoes sold to the number of brand Z shoes sold was 1:2:4.In total,he sold 1/5 of the shoes and earn $840.How many pairs of Brand Z shoes did he have at first?

3)A car & a lorry were heading from Town A to Town B.When the car overtook the lorry,they were 375km away from town B.The car arrived 1h15 min earlier than the lorry which was still 75km away from town B.

a) Find the average speed of the lorry
b) Find the average speed of the car


4)Siti had some red & blue marbles.80% of the marbles were red.After she bought another 63 red marbles & 46 blue marbles,75% of the marbles were red.Find the total number of marbles she had at first.