Q&A - PSLE Math

[mathsparks]

parent135:

i know why this maths paper is more difficult than usual because of 2 reasons:


1)the use of calculators are allowed so the questions will test you more on how to solve the questions instead of calculations.
2)this is the first year of the new format so the questions will be either very difficult or very easy.

Yes, child of parent135, you so clever. Can answer some of my qns below?

mathsparks:

parent135:

fine since everyone is ignoring me im off to do something else and not going to waste time with u lame guys

I've actually logged off to study with son...but..

hi child of parent135, we're not ignoring you. We just find it unusual that you found the paper easy when everyone else is screaming murder. Wonderful for you, you should score full marks and A*. Thanks for sharing with us.

btw, one of my sons' classmate who said it was easy, didn't do well in all his practice papers. So easy doesn't mean the same to everyone.

If you haven't left in a huff, could u at least tell us what school you're from? Have you done yr pri education here in SG? Or was it in China? Did you have good Maths tuition; did you take part in Maths competition? There's a lot we can learn from you. So please share your experience with us. We're not here to bully a small child.

Since you're from China, I guess tomorrow's paper will aslo be easy peasy, right? 1 more A* in your pocket. Hurray!

PS: You sound like a cute fella too!

[dinoegg]

kiasiparent:

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?

[Tang]

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]This is how I solved the question.

http://www.1800-teacher.com/index.php?option=com_kunena&Itemid=59&func=view&catid=24&id=705


This is how my former tuitor solved the question which I think is easier to understand.

http://prischoolmaths.blogspot.com/2009/10/psle-2009-speed.html

[dinoegg]

haha.. i still dont' quite agree to that.. coz by solving that way.. u mean Lim suddenly increase his speed to 20km/h on the last 7 km to achieve the 21 mins time. Sorry my mind is getting old.. still cannot see the valid point..

[Tang]

Removed. Housekeeping.

[dinoegg]

Tang:

dinoegg:

haha.. i still dont' quite agree to that.. coz by solving that way.. u mean Lim suddenly increase his speed to 20km/h on the last 7 km to achieve the 21 mins time. Sorry my mind is getting old.. still cannot see the valid point..

My answer was to move Lim back to the mid-point, hence Mei also had to be moved backwards corresponding. As timeframe was unchanged, it would mean that Mei would take 10.5 minutes more to travel from where she was moved back to to the mid-point. Hence when Lim had completed the race, she would need a total of 21 minutes to reach the finishing line.


Same as my tutor's solution, Kiasuparent has assumed that Lim had continued with his cycling at the costant speed of 20 km/h. Lim travelled another 21 minutes at 20 km/h before Mei finally finished her cycling. [There was no increase in speed for Lim.]

hur ? I think u mixed up Lim and Mei. secondly i don't agree ur assumption on moving Lim to half point and he would only take 10.5mins to cover the 3.5km, coz his speed was definitely slower than 20km/h.

[Tang]

Removed. Housekeeping.

[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