Q&A - PSLE Math

[dinoegg]

Tang:

The distance moved was not 21 km. It was based on whatever speed he was cycling at.

haha.. u r confusing more..

[Tang]

dinoegg:

haha.. u r confusing more..

Sorry to have mixed up Lin and Mei and confused you as I solved the problem the previous day and I have just completed my SA2.

Let me start all over again.


When Lin cycled from start to mid-point,

Mei completed the same distance + 3.5 km.

To cycle the 3.5 km, Mei took 10.5 min. [3.5 km /20 km/h x 60 min/h]

That is, Mei reached the mid-point 10.5 min earlier than Lin.

Conversely, Lin reached the mid-point 10.5 min later than Mei.


Since for half the distance Lin cycled and both cycling at constant speed, he was 10.5 min slower, so for the whole distance Lin would be 21 min slower than Mei. [10.5 min x 2]

Hence Lin reached the finishing line later than Mei by 21 min, i.e. 11.06 a.m. [21 min past 10.45 a.m.]

Have a nice weekend. Bye.

[Lynn2]

You certainly have lots of wisdom.Well said.


All the best to your boy.

Cheers

tianzhu:

Hi James

I hear your roar of concern, but regret that I am unable to tell you more.

My boy looked worried and didn’t want to talk much about the paper and I don’t have the habit of probing for more. The ink on the answer sheets had dried up; and we will learn to accept the outcome, whatever it may be.

Moving forward, we will hold his hands if he stumbles and share his joy if he soars. As parents, we have to face the result, accept it and move on as he continues with his life journey. Like the famous saying in football, we may be a goal down, but the game is over only when we hear the final whistle.

It wouldn’t be polite if I don’t answer your query. But if you look at my previous posts in KSP, other than asking/answering questions, I don’t talk much about other happenings, and I hope you’ll refrain from asking me such questions in the future.

I value my privacy and I hope you’ll understand this.

Best wishes

[mathsparks]

atutor2001:

I am just kidding. I know no one taking PSLE this year. But cannot stand people bragging!


PS

By the way I am not a tutor :lol:

Aiya, atutor2001, everyone so stressed up and you kid around (btw, joke not funny considering how stressed the kids/parents are over the maths paper), plus you're not even a tutor..but out to mislead us eh?

Should at least say you're joking. I was wondering why this tutor lacks empathy.

Actually parent135 is just a smart and confident child and some parents around here are quite harsh to him. He's only P6, please give him a break.

[enoawng]

Mei and Lin take part in a cycling race.

Mei’s speed is 20km/h. When Lin travelled half of the distance, Mei was 3.5km in front of her.
Mei reached finishing line at 10.45am.
What time did Lin reach the finishing line?

21 minutes is correct
<------------------><3>|<---------->|
|--------------------|-----------------------------|
D D
Let S be Lin’s speed. Let D be the halfway distance.
The time whe Lin is halfway is also the time when Mei is 3.5km infront; D/S=(D+3.5)/20
The difference in time to finish the race is
2D/S - 2D/20 = 2(D+3.5)/20-2D/20
= 2D/20+7/20-2D/20=7/20 or 21 minutes

This is a tricky question although the calculation is deceptively simple. It does not seem obvious it can be solved initially as there seems to many unknowns.

I do not think the person who set this question took the same amont of time he/she expects the PLSE student to answer this question. Hence it is not reasonable.

[Augmum]

enoawng, well said........


Moreover, the person who sets this question is an adult but the person who has to solve it is only a 12 years old kid under short limited time :?:

my gal also tried using the algebra approach, but got 2 variables so she tried substituting this and that.....trying to get something out of it but at the end she also cannot remember what she got. she said she spent the most time cracking this question.

[enoawng]

Augmum:

enoawng, well said........


Moreover, the person who sets this question is an adult but the person who has to solve it is only a 12 years old kid under short limited time :?:

my gal also tried using the algebra approach, but got 2 variables so she tried substituting this and that.....trying to get something out of it but at the end she also cannot remember what she got. she said she spent the most time cracking this question.

My son just skipped this question and I took 10-15 minutes before I realized the variables must cancel out. When I was a teenager I was top of my school in maths;-)

If they want to teach model and heuristic approach then they need to set questions to align with the approach. To teach model/heuristic and to set questions beyond that level is bullsxxx.

My future approach will be to get the child to be very proficient in algebra.

[kiasiparent]

dinoegg:

kiasiparent:

[quote=\"N3SKiasu\"]The Speed question (if my DD remembered correctly):


Mei and Lin take part in a cycling race.
Mei's speed is 20km/h. When Lin travelled half of the distance, Mei was 3.5km in front of her.
Mei reached finishing line at 10.45am.
What time did Lin reach the finishing line?

Similar feedback - paper was tough, finished all but not a lot of time left to check through. Anyway, its over now, just move on and focus on next few papers.

So take the total distance to be 2 units.
When Mei travels 1 unit + 3.5km, lim would have travelled 1 unit.
When Mei travels 2 units + 7km, lim would have travelled 2 units. (just finished the race).

So Mei needs to overshot by 7km.

Time = Distance/Speed = 7/20 hours = 7/20 x 60 = 21 minutes.

Lim needs to run 21 mins more.

10.45 + 16 mins = 11.06am

Personally I still find this question 'unanswerable'.. Lim's speed is definitely slower than Mei's speed. So with the Lim's speed left unknown, how to know when Lim will finish the race? The 21mins is the time for Mei to cover the 7km with speed of 20km/h. So Lim will definitely take more than that. Any smart brains to help me clearing my doubts? :)[/quote]For this question, you have to make one assumption and that is both start off the race at the same start line and at the same time.

Hmmm, in the past, PSLE exams were straight forward and all doubts are cleared before they approved the questions to be set. Now, the questions are deliberately set to make the students think hard.

[gifted_indian]

kiasiparent:

For this question, you have to make one assumption and that is both start off the race at the same start line and at the same time.


Hmmm, in the past, PSLE exams were straight forward and all doubts are cleared before they approved the questions to be set. Now, the questions are deliberately set to make the students think hard.

Indeed. Think too hard under a short time. Do you how many P6 kids had sacrificed their social and quality learning time this year, for MONTHS (some even YEARS), just to realise that their PSLE consists of a bunch of unrealistically set questions?

Yes, I say unrealistic since even most of the GEP kids could not even confirm their answer for the last 4 questions. I mean, up till now, have you heard of any parent or student who have said \"I can confidently score Paper 2 this time\" ?

If you haven't, then I think the setters have gone too far beyond what even the smartest brainiest 12-year-old kid in SG can go. Not a fair test I say.

I won't be surprised if some of our maths whizzes would stop pursuing their interest in the subject altogether after this paper. Have the authorities even thought of it? Is assessment, not interest, the number one thing on everyone's minds in SG?

[Vanilla Cake]

MummyJamie:

Ohh! And for paper one, the second last question, the computer one, what did ya'll get?

I got 100 minutes. Many are saying it's 25.
o_o

PSLE Maths 2009 Paper 1 Q29 (Not in exact words)
6 friends decided to rent computers from 2 to 4.30 pm.While 4 of them were playing, the other 2 would watch.If the cycle continued, how much playtime would each person get?\t

Suggested solution
From 2 pm to 4.30 pm -> 2 h 30 min = 150 min\t\t
4 x 150 = 600 (Total for 4 computers since there were 4 players)\t\t
600 / 6 = 100 min\t\t
Amount of playtime that each person get was 100 min