Q&A - PSLE Math

[MathIzzzFun]

small:

Brain stuck, please help and TIA..


A car and a loory started at the same time and travelled from Town R to Town S along the same route, When the car arrived in Town S 45 min ealier than the lorry, the lorry had only just travelled 3/5 of the journey. If the averagespped of the lorry was 60 km/h, find the distance between the two towns.

Hi

The car reached Town S 45 min earlier which also means that the lorry will take another 45 min to reach Town S ... speed of lorry is known, so the distance to Town S can be calculated and this is equal to 2/5 of the journey.. I think you complete the solution

cheers.

[small]

MathIzzzFun:

small:

Brain stuck, please help and TIA..


A car and a lorry started at the same time and travelled from Town R to Town S along the same route, When the car arrived in Town S 45 min ealier than the lorry, the lorry had only just travelled 3/5 of the journey. If the average speed of the lorry was 60 km/h, find the distance between the two towns.

Hi

The car reached Town S 45 min earlier which also means that the lorry will take another 45 min to reach Town S ... speed of lorry is known, so the distance to Town S can be calculated and this is equal to 2/5 of the journey.. I think you complete the solution

cheers.

Hi MathIzzzFun,

Thanks for the solution..

By the way, can you please explain why the lorry will also take another 45 min to reach Town S if the speed of the 2 vehicles not the same?

[tianzhu]

Hi small


Good Morning.

Hope this helps.

Best wishes

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

[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!!!