Q&A - PSLE Math

[MathIzzzFun]

small:

Need some advice and thanks in advance.


Question:
There are 42 pupils in each of the classes, Primary 5A and Primary 5B. The ratio of the number of boys in Primary 5A to the number of boys in Primary 5B was 3:4. The ratio of the number of girls in Primary 5A to the number of girls in Primary 5B was 4:3. There were 56 boys altogether in both classes.
What was the ratio of boys in Primary 5A to the number of girls in Primary 5B?
(Given answer is 1:1 but my DS’s answer is 12:5)

Hi small,

The question is ambiguous - 2 possible answers.

1)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

From 5A = B B B G G G G = 42 => G =6
5B = B B B B G G G = 42 => B = 6
So, G = B = 6

Ratio of 5A boys to 5B girls = 1: 1

2)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

Given total number of boys = 56
so 7B = 56, B =8, G=4

5A boys : 5B girls = 3 x 8 : 3 x 4 = 2 : 1

cheers.

[ozora]

tianzhu:

Hi


For Q1,you may use Systematic Listing by working out a list of equivalent ratios.
You may also use the concept of “Two changed quantities”

In this illustration, I am using UM, basing on the concept that the total value of coins remains the same before and after.

As for Q2, please refer to the underlined sentence, you may wish to check your source again.

Shop A has 164 more customers than shop B . After 1/4 of the customers in shop A and went to shop B, there was 48 more customers in shop A than in shop A. How many customers were there in shop A and shop B respectively?

I think there are are some missing words in this sentence.Also,it should read as “there were 48 more customers in shop A than in shop B”. The question is also a bit vague, does the number of customers refer to the before or after scenarios. I’ve worked out both.

May I take this opportunity to wish all mothers in KSP a very “Happy Mother’s Day”
And to the two very wonderful women in my life, Thank you for all your support.

Best wishes

http://farm4.static.flickr.com/3452/5694122509_6194739b94_z.jpg\">

http://farm4.static.flickr.com/3281/5694695728_6ab3d5b56a_z.jpg\">

thanks for the guide.
sorry for the mistake I made. It is actually \"there were 48 more customers in shop B than in shop A”.

[small]

MathIzzzFun:

small:

Need some advice and thanks in advance.


Question:
There are 42 pupils in each of the classes, Primary 5A and Primary 5B. The ratio of the number of boys in Primary 5A to the number of boys in Primary 5B was 3:4. The ratio of the number of girls in Primary 5A to the number of girls in Primary 5B was 4:3. There were 56 boys altogether in both classes.
What was the ratio of boys in Primary 5A to the number of girls in Primary 5B?
(Given answer is 1:1 but my DS’s answer is 12:5)

Hi small,

The question is ambiguous - 2 possible answers.

1)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

From 5A = B B B G G G G = 42 => G =6
5B = B B B B G G G = 42 => B = 6
So, G = B = 6

Ratio of 5A boys to 5B girls = 1: 1

2)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

Given total number of boys = 56
so 7B = 56, B =8, G=4

5A boys : 5B girls = 3 x 8 : 3 x 4 = 2 : 1

cheers.

Hi MathIzzzFun,

Many thanks for your time.

[MathIzzzFun]

small:

MathIzzzFun:

[quote=\"small\"]Need some advice and thanks in advance.


Question:
There are 42 pupils in each of the classes, Primary 5A and Primary 5B. The ratio of the number of boys in Primary 5A to the number of boys in Primary 5B was 3:4. The ratio of the number of girls in Primary 5A to the number of girls in Primary 5B was 4:3. There were 56 boys altogether in both classes.
What was the ratio of boys in Primary 5A to the number of girls in Primary 5B?
(Given answer is 1:1 but my DS’s answer is 12:5)

Hi small,

The question is ambiguous - 2 possible answers.

1)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

From 5A = B B B G G G G = 42 => G =6
5B = B B B B G G G = 42 => B = 6
So, G = B = 6

Ratio of 5A boys to 5B girls = 1: 1

2)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

Given total number of boys = 56
so 7B = 56, B =8, G=4

5A boys : 5B girls = 3 x 8 : 3 x 4 = 2 : 1

cheers.

Hi MathIzzzFun,

Many thanks for your time. :)[/quote]Hi small,

you are welcome :lol:

cheers.

[MathIzzzFun]

small:

MathIzzzFun:

[quote=\"small\"]Need some advice and thanks in advance.


Question:
There are 42 pupils in each of the classes, Primary 5A and Primary 5B. The ratio of the number of boys in Primary 5A to the number of boys in Primary 5B was 3:4. The ratio of the number of girls in Primary 5A to the number of girls in Primary 5B was 4:3. There were 56 boys altogether in both classes.
What was the ratio of boys in Primary 5A to the number of girls in Primary 5B?
(Given answer is 1:1 but my DS’s answer is 12:5)

Hi small,

The question is ambiguous - 2 possible answers.

1)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

From 5A = B B B G G G G = 42 => G =6
5B = B B B B G G G = 42 => B = 6
So, G = B = 6

Ratio of 5A boys to 5B girls = 1: 1

2)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

Given total number of boys = 56
so 7B = 56, B =8, G=4

5A boys : 5B girls = 3 x 8 : 3 x 4 = 2 : 1

cheers.

Hi MathIzzzFun,

Many thanks for your time. :)[/quote]Hi small,

you are welcome :lol:

cheers.

[MathIzzzFun]

bobsg01:

http://i53.tinypic.com/9px7c7.jpg\">


Answer given was $655

But have problem how it was derived.

Hope after today, the MOE will do some self reflection on S'pore PSLE math. It's really tough for our young child.

Hi bobsg01

hope this helps

http://www.flickr.com/photos/62167097@N02/5697131686/in/photostream

cheers.

[small]

MathIzzzFun:

Need some advice and thanks in advance.


Question:
There are 42 pupils in each of the classes, Primary 5A and Primary 5B. The ratio of the number of boys in Primary 5A to the number of boys in Primary 5B was 3:4. The ratio of the number of girls in Primary 5A to the number of girls in Primary 5B was 4:3. There were 56 boys altogether in both classes.
What was the ratio of boys in Primary 5A to the number of girls in Primary 5B?
(Given answer is 1:1 but my DS’s answer is 12:5)

[quote]Hi small,

The question is ambiguous - 2 possible answers.

2)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

Given total number of boys = 56
so 7B = 56, B =8, G=4

5A boys : 5B girls = 3 x 8 : 3 x 4 = 2 : 1]

cheers.[/quote]
Hi MathIzzzFun,

Sorry, solution 2 looks logical but I think the answer is incorrect.

Given total number of boys = 56
so 7B = 56, B =8, G=4

Base on this, my DS said:
5A = B B B G G G G = 24 + 16 = 40
5B = B B B B G G G = 32 + 12 = 44
:oops:

Can you please help again ? Many thanks in advance.

[MathIzzzFun]

small:

MathIzzzFun:

Need some advice and thanks in advance.


Question:
There are 42 pupils in each of the classes, Primary 5A and Primary 5B. The ratio of the number of boys in Primary 5A to the number of boys in Primary 5B was 3:4. The ratio of the number of girls in Primary 5A to the number of girls in Primary 5B was 4:3. There were 56 boys altogether in both classes.
What was the ratio of boys in Primary 5A to the number of girls in Primary 5B?
(Given answer is 1:1 but my DS’s answer is 12:5)

[quote]Hi small,

The question is ambiguous - 2 possible answers.

2)
5A = B B B G G G G = 42
5B = B B B B G G G = 42
Total 7B + 7G = 84, B+G= 84/7 = 12

Given total number of boys = 56
so 7B = 56, B =8, G=4

5A boys : 5B girls = 3 x 8 : 3 x 4 = 2 : 1]

cheers.

Hi MathIzzzFun,

Sorry, solution 2 looks logical but I think the answer is incorrect.

Given total number of boys = 56
so 7B = 56, B =8, G=4

Base on this, my DS said:
5A = B B B G G G G = 24 + 16 = 40
5B = B B B B G G G = 32 + 12 = 44
:oops:

Can you please help again ? Many thanks in advance.[/quote]Hi small,

you are right, must be having mid-night blues :lol:

Seems that there is no answer in this case, cos for solution 1, B = G = 6 => Total number of boys = 42 instead of 56.

cheers.

[bobsg01]

Hi MathIzzzFun,


Thanks you.

:boogie: :boogie: :boogie:

[MathIzzzFun]

bobsg01:

Hi MathIzzzFun,


Thanks you.

:boogie: :boogie: :boogie:

hi bobsg01,

avec plaisir :lol:

cheers.