Q&A - PSLE Math

[Dharma]

kancheongmum:

Hi all need help

Raju drove at a constant speed from his house to Town B. On his way, he passed Town A. At 9.20 am he was 383 km from Town B and 205 km from Town A. At 12.50pm, he stopped at a petrol kiosk which was midway between Town A and Town B. At what speed did Raju drive before he came to the petrol kiosk? (ans 84km/h)
Thank you.

Distance = [205 + (383 - 205)/2]km = 294km
Speed = 294km/ 3.5hrs = 84km/hr

[tianzhu]

Hi Dharma


Good Morning

I think this question may cause problems to some students.

205km from Town A?
Is it 205km before Town A or after Town A?

To get 84km/h,a student has to interpret it as 205km before Town A, maybe it’s the intention of the question setter.

Best wishes

[ruohoo97]

Dharma:

kancheongmum:

Hi all need help

Raju drove at a constant speed from his house to Town B. On his way, he passed Town A. At 9.20 am he was 383 km from Town B and 205 km from Town A. At 12.50pm, he stopped at a petrol kiosk which was midway between Town A and Town B. At what speed did Raju drive before he came to the petrol kiosk? (ans 84km/h)
Thank you.

Distance = [205 + (383 - 205)/2]km = 294km
Speed = 294km/ 3.5hrs = 84km/hr

I didn't get it. the distance traveled from 9.20 to 12.50 should be (205+383)/2 -205=89 km, thus:
the speed will be 89/3.5=25.4km/h
???

[Dharma]

tianzhu:

Hi Dharma


Good Morning

I think this question may cause problems to some students.

205km from Town A?
Is it 205km before Town A or after Town A?

To get 84km/h,a student has to interpret it as 205km before Town A, maybe it’s the intention of the question setter.

Best wishes

Good morning Tianzhu.

Below is my interpretation.


http://www.postimage.org/image.php?v=TsMZA80

[kancheongmum]

Hi all

Good morning, you all sure wake up very early.
Yes some students may have problems in the interpretation of the question. My ds interpret as the 205 km is after Town A. His reason is the sentence ‘On his way, he passed Town A.’ So he did not get the answer 84 km/h. I interpret that way too at first but after some thoughts it doesn’t not make sense to drive at such low speed 3.5 hrs you only cover 89 km. For us, we will reason that way because we drive but for a 12 yr old may not be and under the pressure of examination. This question is from his prelmin 2 Maths paper and is a 4 marks question. He got 1mark for lst part of the working. I feel this is an unfair question and the interpretation of 205km after Town A is not all wrong. I really hope things like that will not happen in PSLE. Poor kids under so much pressure and so much reasoning to do. All other feel free to give your view. Thank you.

[tianzhu]

kancheongmum:

My ds interpret as the 205 km is after Town A. His reason is the sentence 'On his way, he passed Town A.

Hi kancheongmum
Good Morning

Your boy has brought up a logical point.

What was in the mind of the setter when the question was crafted?

I think the best person to check is his school teacher.

Best wishes

[leesf]

Hi, appreciate your help on this Red Swastika 2009 CA1 question.



http://www.postimage.org/image.php?v=aVulXk9

[Dharma]

leesf:

Hi, appreciate your help on this Red Swastika 2009 CA1 question.



http://www.postimage.org/image.php?v=aVulXk9

Ratio of area of W : X : Y = 5 : 20 : 28

Area of (W + Y) = Area of (X + Z)
5u + 28u = 20u + 52
13u = 52
1u = 4
Area of rectangle PQRS = 33u x 2 = 33 x 4 x 2 = 264
Area of rectangle PQRS is 264cm2

[Vanilla Cake]

leesf:

Hi, appreciate your help on this Red Swastika 2009 CA1 question.


http://www.postimage.org/image.php?v=aVulXk9

W : X
1 : 4

X : Y
5 : 7

W : X : Y
5 : 20 : 28

W+Y is half the rectangle ie X+Z is the other half
Z = (28u+5u)-20u = 13u
13u -> 52
u -> 4
66u -> 264

Area of rectangle PQRS = 264 cm²

Hi leesf,
Have you bought the 2010 P6 Prelim Maths papers from top schools?

[leesf]

Thanks Dharma & Vanilla cake for the solutions. No, I did not get the 2010 papers. Its only a month a way from PSLE. I’m letting my son to revise those questions which he tends to make mistakes.