Primary school maths: A vicious circle (from TODAY May 8)
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sean wife:
Think this is the answer to part 2. I also got the same answer...my method is to divide the distance between town a and b into 5 parts.... Actually part and b can be solved in the same way right, except starting time and time taken is different...[/quote]
Think Alan wld have walked beyond town B by 2.56pmNebbermind:
[quote=\"wonderm\"]
Is the answer 2.56pm?
Answer to 1st part is 2.38pm? -
Oops, wasn’t paying attention in class!
But I thought this kind ratio/speed qns is quite standard? Seen a lot being asked in academic threads -
Edureach:
Strparent:
errr, paiseh so many good long post on this thread, but pardon me, can I stray back on-topic on pr sch maths - esp. on setting questions beyond the standard syllabus...?
I have always try to let my kids learn on their own, from sch, from friends, from teachers, but never from tutors on maths.
today I look at my DD's maths SA1 paper, which she got zero for a 5-mark question. At first glance, I blew up and questioned on how she could not get it even partially right ? 5 marks wor, why ? no time ? nervous ? careless ? cant remember formula / method ?
the question looked straight forward enough, so I asked her to take a paper and started to show her how to solve it. After 10sec, I was stumped. LOL. So I tiam tiam, act cool a bit, ask my DS to come over ( incidentally he is in Sec2 and was always fantastic in maths ). Guess what ? It took him 15mins of pondering, writing and cancelling, before he eventually started to solve the question. But the workings were like so messy and mixed up, so I asked him to explain to his sister. He tried to explain, but DD catch no ball. In the meantime, I was trying to comprehend his work, and figured out how the solution was derived.
But I know there and then, that DD never learnt this in sch, it looks like something DS do in Maths Olympiad during his P5/P6 days.
Now I am in agreement with most parents about no unnecessary pressure or workload, no tuition, etc, but now I noted that the schools DO set questions beyond the syllabus, which is ridiculous. If you taught it, fine - of course some of her classmates get full marks for the paper.
So, yes, MOE should note this and if you want to set the standards higher, then make sure the schools teach the students as well, and not depend or expect all to learn them elsewhere.
The question which I paiseh to say, had me stumped until DS showed me the solution.
It looked to me initially like some parameters is lacking :oops:
Alan took 1/2 hr to walk from Town A to Town B at a constant speed.
Eric took 3/4 hr to walk from Town B to Town A at a constant speed.
Both started at 2.20pm.
a) at what time did Alan and Eric pass each other along the way ?
b) at the precise time when Alan reached Town B, Steven started walking from Town A to Town B at the same constant speed as Alan. At what time, did Steven and Eric meet ?
maybe it's just me, but share with me , if you think it is STANDARD primary sch maths ?
Could hve used model drawing, but simply lazy.
Speed of Allan - 30 mins.
Speed of Eric - 45 mins.
Ratio 3:5
Divide the distance into 5 units.
Each unit of Allan represent 6mins x 5 = 30mins
Each unit of Eric represent 9 mins x 5 = 45 mins.
Allan travelled from pt A to B
Eric travelled from pt B to A
Allan would had covered 3 units vs 2 for Eric.
So the time they met would be 2.20 + 18mins = 2.38pm. Ans (a)
Allan would reached pt A at 2.50pm.
Eric would had covered 30/45 mins.
Speed of Steven was similar to Allan- 30mins.
Steven would had met Eric at 2.50 + 6mins= 2.56pm Ans (b) as Eric would had reached pt A at 3.05pm. Good night! :rahrah:
I thought ratio of speed should be 3:2...?? -
sean wife:
Edureach:
[quote=\"Strparent\"]errr, paiseh so many good long post on this thread, but pardon me, can I stray back on-topic on pr sch maths - esp. on setting questions beyond the standard syllabus...?
I have always try to let my kids learn on their own, from sch, from friends, from teachers, but never from tutors on maths.
today I look at my DD's maths SA1 paper, which she got zero for a 5-mark question. At first glance, I blew up and questioned on how she could not get it even partially right ? 5 marks wor, why ? no time ? nervous ? careless ? cant remember formula / method ?
the question looked straight forward enough, so I asked her to take a paper and started to show her how to solve it. After 10sec, I was stumped. LOL. So I tiam tiam, act cool a bit, ask my DS to come over ( incidentally he is in Sec2 and was always fantastic in maths ). Guess what ? It took him 15mins of pondering, writing and cancelling, before he eventually started to solve the question. But the workings were like so messy and mixed up, so I asked him to explain to his sister. He tried to explain, but DD catch no ball. In the meantime, I was trying to comprehend his work, and figured out how the solution was derived.
But I know there and then, that DD never learnt this in sch, it looks like something DS do in Maths Olympiad during his P5/P6 days.
Now I am in agreement with most parents about no unnecessary pressure or workload, no tuition, etc, but now I noted that the schools DO set questions beyond the syllabus, which is ridiculous. If you taught it, fine - of course some of her classmates get full marks for the paper.
So, yes, MOE should note this and if you want to set the standards higher, then make sure the schools teach the students as well, and not depend or expect all to learn them elsewhere.
The question which I paiseh to say, had me stumped until DS showed me the solution.
It looked to me initially like some parameters is lacking :oops:
Alan took 1/2 hr to walk from Town A to Town B at a constant speed.
Eric took 3/4 hr to walk from Town B to Town A at a constant speed.
Both started at 2.20pm.
a) at what time did Alan and Eric pass each other along the way ?
b) at the precise time when Alan reached Town B, Steven started walking from Town A to Town B at the same constant speed as Alan. At what time, did Steven and Eric meet ?
maybe it's just me, but share with me , if you think it is STANDARD primary sch maths ?
Could hve used model drawing, but simply lazy.
Speed of Allan - 30 mins.
Speed of Eric - 45 mins.
Ratio 3:5
Divide the distance into 5 units.
Each unit of Allan represent 6mins x 5 = 30mins
Each unit of Eric represent 9 mins x 5 = 45 mins.
Allan travelled from pt A to B
Eric travelled from pt B to A
Allan would had covered 3 units vs 2 for Eric.
So the time they met would be 2.20 + 18mins = 2.38pm. Ans (a)
Allan would reached pt A at 2.50pm.
Eric would had covered 30/45 mins.
Speed of Steven was similar to Allan- 30mins.
Steven would had met Eric at 2.50 + 6mins= 2.56pm Ans (b) as Eric would had reached pt A at 3.05pm. Good night! :rahrah:
I thought ratio of speed should be 3:2...??[/quote]You are correct. Typo error on my part. -
sean wife:
EduReach, seanwife,
Think this is the answer to part 2. I also got the same answer...my method is to divide the distance between town a and b into 5 parts.... Actually part and b can be solved in the same way right, except starting time and time taken is different...
thanks for making the solution so freaking simple. the funny thing is, the teacher gave them a correction solution slightly differently, instead of this clear simple-to-understand model solution.
1min
A --> 1/30 km
E --> 1/45 km
} 1/18 km
18/1 = 18mins
a) 2.20pm ------> 2.38pm ANS.
and so on for (b)
:scratchhead: :scratchhead:wonderm:
Wonderm,This is a very interesting question. If one were to use algebra (Sec level maths) to solve, it is actually much more lengthy and less elegant than using model method.
it challenges those who are good in maths, and really shows how a seemingly difficult or impossible question can be very easily solved by drawing a simple model. If we expect the teacher to have given similar questions in class before the test, it really becomes pointless and makes learning maths much more painful as the children would think they need to remember the methods for all different kinds of questions.
thank you for the enlightened statements.
I admit - I have always been an opposition of the models method. Absolutely hate it, because I keep telling my kids that they do not use this anymore in sec sch, so for them, I would tell them to use algebra since P5.
and hence this question stumped me, becoz I tried to make a direct question complicated ! :oops: After seeing how simple Edureach explained the solution, I have been humbled by models today. :gloomy:
DS never had this issue, because so far, algebra solves most questions quicker for him during P5/P6. His teachers accepted it, but DD teacher always argued that she cannot use algebra, preferably models and units.
Thanks again all. -
Quote
EduReach, seanwife,
thanks for making the solution so freaking simple. the funny thing is, the teacher gave them a correction solution slightly differently, instead of this clear simple-to-understand model solution.
1min
A –> 1/30 km
E –> 1/45 km
} 1/18 km
18/1 = 18mins
a) 2.20pm ------> 2.38pm ANS.
and so on for (b)
Both solutions are correct and can be used. The teacher’s solution is better cos it is time saving and based on average travelling time. The ratio method is easier for the students to understand the concept and I usually teach this method when they have problem understanding the teacher’s method. Of course in the end, they should use the teacher’s method. -
Strparent:
EduReach, seanwife,
thanks for making the solution so freaking simple. the funny thing is, the teacher gave them a correction solution slightly differently, instead of this clear simple-to-understand model solution.
1min
A --> 1/30 km
E --> 1/45 km
} 1/18 km
18/1 = 18mins
a) 2.20pm ------> 2.38pm ANS.
and so on for (b)
:scratchhead: :scratchhead:
Not sure is the \"km\" given by the teacher. If yes, then the concept is wrong. It should be \"of the total distance\".
Teacher's method is thinking out of the box, treating it like those question where tap A fills a tank in 30 min and tap B fills a tank in 45 min. So it is a more intelligent method i.e. a short cut.
Model method is heuristic i.e. using logic and following the development of the question. -
Strparent:
How to get 1/18?
A --> 1/30 km
E --> 1/45 km
} 1/18 km
18/1 = 18mins -
laughingcat:
By adding 1/30 & 1/45. like at2001 said, it is not in km but perhaps U, where U is the dist between town A and B.
How to get 1/18?Strparent:
A --> 1/30 km
E --> 1/45 km
} 1/18 km
18/1 = 18mins -
Strparent:
Alternative method (similar to your dd teacher's method):
Alan took 1/2 hr to walk from Town A to Town B at a constant speed.
Eric took 3/4 hr to walk from Town B to Town A at a constant speed.
Both started at 2.20pm.
a) at what time did Alan and Eric pass each other along the way ?
b) at the precise time when Alan reached Town B, Steven started walking from Town A to Town B at the same constant speed as Alan. At what time, did Steven and Eric meet ?
a) Let distance between Town A and B be D.
Alan's speed = D/1/2 = 2D
Eric's speed = D/3/4 = 4/3D
Combined speed = 10/3D
Time taken to meet = Distance/combined speed
= D/(10/3D) = 3/10 hr = 18min
So they met 18mins after 2.20pm at 2.38pm
b) When Alan reached Town B, Eric had traveled 30/45 or 2/3 of journey, so left 1/3 of journey.
Applying same method as in (a) but using 1/3D instead of D,
time taken to meet = 1/3 x 18 = 6min
Steven started at 2.20pm + 30 min = 2.50pm
So they met 6mins after 2.50pm at 2.56pm.
Hope this helps.
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