Q&A - PSLE Math

[small]

tianzhu:

Hi small


Good Morning.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7146/6578211687_96541f06a3_z.jpg\">

lol, my son and I think too much.

Anyway Tianzhu & MathIzzfun, once again many thanks for your help.

[MathIzzzFun]

small:

tianzhu:

Hi small


Good Morning.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7146/6578211687_96541f06a3_z.jpg\">

lol, my son and I think too much.

Anyway Tianzhu & MathIzzfun, once again many thanks for your help.

u r welcome

cheers!

[Chan09]

Can someone advise on nanyang ca1 Primary 6 maths 2011 question 18 as there seems to be a missing part in the paper?


The total area of triangle A and B is ??? Of the area of triangle c? Thank you

[Neat]

Hi


I would like to know the working for the following question:

1) The ratio of the number of Donovan’s stickers to the number of Hong Yi’s stickers is 10:3. After Donovan gave Hong Yi 1/5 of his stickers, Hong Yi had 30 stickers less than Donovan. How many stickers did Donovan give to Hong Yi?

2) Class A and Class B have the same number of pupils. The ratio of the number of boys in Class A to the number of boys in Class B is 3:2. The ratio of the number of girls in Class A to the number of girls in Class B is 3:5. Find the ratio of the number of boys in Class A to the number of girls in Class B.

By the way, is there any book to recommend on the ratio problems?

Thanks so much for the help.

[tianzhu]

Hi


Good Morning.

I’ll do Q2 first.

In this question, a student needs to see that the ratios representing the boys and girls are of different measures and kinds. One needs to differentiate the ratios showing boys and girls.

Let’s have units for boys and parts for girls.MD would come in handy for this question. Due to time constraints, I am not drawing it, but shall give you some pointers.

Boys ----- A : B ------ 3u : 2u
Girls ----- A : B ------ 3p : 5p

Class A and Class B have the same number of pupils.

3u + 3p ----- 2u + 5p
Hence, 1u ----- 2p

Boys ----- A : B ------ 6p : 4p
Girls ----- A : B ------ 3p : 5p

The ratio of the number of boys in Class A to the number of girls in Class B ----- 6:5

As for Q1, you may choose to work using MD or UM.

At first
D : HY ----- 10 : 3

D gave HY 1/5 of his stickers or 2 units

In the end
D : HY ----- 8 : 5

3 units ---- 30
1 unit ----- 10

2 units ----- 20

Best wishes

[just888]

Neat:

1) The ratio of the number of Donovan's stickers to the number of Hong Yi's stickers is 10:3. After Donovan gave Hong Yi 1/5 of his stickers, Hong Yi had 30 stickers less than Donovan. How many stickers did Donovan give to Hong Yi?

1/5 of 10 units is 2 .
After giving Donovan's stickers : HongYi's stickers is 8:5
Difference in units is 3.
3 units = 20 stickers
1 units 10.
Donovan gives Hong Yi 2 unit therefore, 2x10 = 20 stickers.

Neat:

2) Class A and Class B have the same number of pupils. The ratio of the number of boys in Class A to the number of boys in Class B is 3:2. The ratio of the number of girls in Class A to the number of girls in Class B is 3:5. Find the ratio of the number of boys in Class A to the number of girls in Class B.

Class A boys to Class B boys is 3:2
Class A girls to Class B girls is 3:5

Common multiple of 2, 3, 5 is 30. Therefore:

Class A boys to Class B boys is : 10:15
Class A girls to Class B girls is : 10: 6

Hence, Class A boys to Class B girls is 10:6

[Neat]

tianzhu:

Hi


Good Morning.

I’ll do Q2 first.

In this question, a student needs to see that the ratios representing the boys and girls are of different measures and kinds. One needs to differentiate the ratios showing boys and girls.

Let’s have units for boys and parts for girls.MD would come in handy for this question. Due to time constraints, I am not drawing it, but shall give you some pointers.

Boys ----- A : B ------ 3u : 2u
Girls ----- A : B ------ 3p : 5p

Class A and Class B have the same number of pupils.

3u + 3p ----- 2u + 5p
Hence, 1u ----- 2p

Boys ----- A : B ------ 6p : 4p
Girls ----- A : B ------ 3p : 5p

The ratio of the number of boys in Class A to the number of girls in Class B ----- 6:5

As for Q1, you may choose to work using MD or UM.

At first
D : HY ----- 10 : 3

D gave HY 1/5 of his stickers or 2 units

In the end
D : HY ----- 8 : 5

3 units ---- 30
1 unit ----- 10

2 units ----- 20

Best wishes

:rahrah: :rahrah: :rahrah:
Hi Tianzhu,

So the answer sheet is incorrect for Q1, it is stated as 29.

Thank you so much!!!

[Neat]

just888:

Neat:

1) The ratio of the number of Donovan's stickers to the number of Hong Yi's stickers is 10:3. After Donovan gave Hong Yi 1/5 of his stickers, Hong Yi had 30 stickers less than Donovan. How many stickers did Donovan give to Hong Yi?

1/5 of 10 units is 2 .
After giving Donovan's stickers : HongYi's stickers is 8:5
Difference in units is 3.
3 units = 20 stickers
1 units 10.
Donovan gives Hong Yi 2 unit therefore, 2x10 = 20 stickers.

Neat:

2) Class A and Class B have the same number of pupils. The ratio of the number of boys in Class A to the number of boys in Class B is 3:2. The ratio of the number of girls in Class A to the number of girls in Class B is 3:5. Find the ratio of the number of boys in Class A to the number of girls in Class B.

Class A boys to Class B boys is 3:2
Class A girls to Class B girls is 3:5

Common multiple of 2, 3, 5 is 30. Therefore:

Class A boys to Class B boys is : 10:15
Class A girls to Class B girls is : 10: 6

Hence, Class A boys to Class B girls is 10:6

Hi just888

Thanks for help.

The answer for Q2 is 6:5.

[tianzhu]

Neat:

:rahrah: :rahrah: :rahrah:
Hi Tianzhu,
Thank you so much!!!

Hi Neat

Good Morning.

You're welcome.

Hope this helps.

Best wishes.

http://farm8.staticflickr.com/7142/6623800383_1c4c031586_z.jpg\">

[just888]

tianzhu:

Neat:

:rahrah: :rahrah: :rahrah:
Hi Tianzhu,
Thank you so much!!!

Hi Neat

Good Morning.

You're welcome.

Hope this helps.

Best wishes.

http://farm8.staticflickr.com/7142/6623800383_1c4c031586_z.jpg\">

Tianzhu,
Thanks for the clear explaination. Guess I need to re-study my math too.