Q&A - PSLE Math

[Maths Monster]

Budo:

Hi need help in this question


Andrew and Brian had some money
If Andrew gave Brian $55, the ratio of Andrew to Brian amount is 3:5.
If Brian gave Andrew 20% of this money and $10, Andrew would have $108 more than Brian.
How much do Andrew and Brian have at first?

If Andrew gave Brian $55, the ratio of Andrew to Brian amount is 3:5.
A [3u]
B [5u]

At start,
A [3u+55]
B [5u-55]

If Brian gave Andrew 20% of this money and $10, Andrew would have $108 more than Brian. 20% of 55 + 10 = $21
A [3u+55+21] = [3u+76]
B [5u-55-21] = [5u-76]

We can write the equation:
3u+76-108 = 5u-76
2u = 44
u =22

Therefore, at first,
A = 3u+55 = $121
B = 5u-55 = $55
Total = $176

[hamsterss]

livewith_vanilla:

hamsterss:

[quote=\"ruyu\"]

[/quote]
Really? I saw the Maths Workbook 6B's answer key wrote the answer as :

1000+2000=3000km [Example]

Is it okay since the answer key in the Maths Workbook 6B wrote it this way?

One more :oops:

Can i just write :

100m + 3km = 3.1km? even though the unit is not the same?

Thanks

[ruyu]

hamsterss:

livewith_vanilla:

[quote=\"hamsterss\"]

[/quote]
sorry cannot. Marks will be deducted. You have to do something like this:

3km = 3000m

100m+3000m= 3100m

3100m=3.1km


Yeah this is the way. Dont need to write final statement waste time.Do live_vanillacake way

[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