Q&A - PSLE Math

[MathIzzzFun]

Maths Isnt Fun:

MathIzzzFun:

[quote=\"daranic\"]Qn appears in today's Maths paper 2:


Alex and Bob were racing around a 400m track. Alex ran at a speed of 190m/min. Bob ran at a speed 25m/min lesser than Alex. How many complete rounds must Alex run to run 300m more than Bob?

Hi

I take it that both Alex and Bob started to run at the same time. To build up a gap of 300m, Alex needs to run for at least 300 m / 25m/min = 12 min ie total distance of 12 min x 190 m/min = 2280m or 2280/400 = 5.7 --> 6 complete rounds needed to be at least 300 m ahead.

cheers.

Hey today i took the maths psle and i guess it was like average? Well, for this question i put 5 because they said complete rounds so if its 5.7, the max number of complete rounds is only 5. [/quote]hi

It depends on how the question is phrased. For eg. if the question ask : \"after some time, Alex was 300m ahead of Bob. How many complete rounds did Alex complete?\" , then answer would be 5.

but if the question is asking : \" how many complete rounds must Alex run to be 300 m ahead of Bob?\" then the answer should be 6.

*just read the PSLE thread which puts the question as:
Alex and Benny and running around a track measuring 400m.
Alex travels at 190m/min, 25m/min faster than Benny.
If Alex is faster than Benny by 300m, how many COMPLETE rounds have he completed by that time?
- in this case, answer is 5.*


cheers.

[cylg]

Maths Isnt Fun:

For the last and second last question of maths PSLE does anyone rmb the question? I only remembered my answers but not the questions... ==\"

If my DS recalled correctly...

Paper 2

Qn 17-

School X was holding a event and tickets were as follows:
Teacher - $20
Student - $8

1/4 of the tickets were bought by teachers. The total cost of tickets bought by the students was $416 more than the total cost of the tickets bought by the teachers. What was the total cost of all the tickets purchased.

Ans: $4576 (At least thats what my DS said)

Qn 18 -

Mr Z had $X. he spent 1/4 of his money on something and 2/5 of the remainder on something else. After that, his parents gave him $120. In the end, the ratio of the amt of money he had in the end to the amt of money he had in the beginning was 5:4. Find $X.

Ans: $150

Hope that helps

[ivanhoo99]

All our difficult question posted on kiasuparents Q&A Maths and PSLE Discussion are all answered by the masters of maths...


Thank you so much for your kind support!!

[KiasuAdult]

Maths Isnt Fun:

Who noes how to do the question in paper two abt the tiles? For part a my ans was 5/9 and for part b my ans was 180m2. Also, the question before that was abt the chairs. It was something like this...: Someone arranged chairs in a hall and each row had exactly 9 chairs. He then bought 6 chairs and changed the number of chairs in each row to 7.He had 12 extra rows in the end. How many chairs did he have in the hall? I was stuck at this for awhile but i worked it out and my ans was 351

for the tiles q i put the same ans as you i think it's correct. for the chairs i put 357 because cos the q ask how many chairs were there for the concert and for the concert he brought in the 6 chairs.

[JACLC]

If anyone can remember the exact words in the reading question, please post here. The questions were not very clear.

[chrisu]

I read from the other forum that if she start reading from Friday, then I ageed it's 24 days instead of 26.

MathIzzzFun:

chrisu:

If can selectively choose weekend to read, then why not 525/30 = 17.5. Thus the least no. of days would become 18 days which is not among the mcq answers. I think the answer should be 26days.

Hi

the question aims to mislead students to start on Mon which will give the answer as 26 days.. however, if the reading starts on Fri, we will arrive at the least number of days which is 24 days.

cheers.

[/quote]


Yea i guess its meant to mislead but if it is, the setters might as well add an 18 to one of the options. I wasnt rlly sure abt my ans for this question but i put 26 days[/quote]

[daranic]

Anyone knows if the problem was solved using guess & check, instead of the usually method (ie, eg. units, models etc), will it be considered full marks as long as the answer is correct?

[NickleBee Tutors]

daranic:

Anyone knows if the problem was solved using guess & check, instead of the usually method (ie, eg. units, models etc), will it be considered full marks as long as the answer is correct?

Don't worry. \"Guess and Check\" us a perfectly useful Heuristic Method as recognized by MOE and in fact is listed in Poyla's list of problem solving techniques. As long as your \"Guess and Check\" working is legible and laid out in a logical and sequential manner (not scribbled all over the place), you should be able to get the full method marks and answer mark.

However if there is no clear working done when doing the \"Guess and Check\" technqiue (ie only rough scribbles all over which is also known as \"no head no tail\" working and finally an answer written at the bottom), i'm afraid its up to the discretion of the PSLE marker to award method marks if any.

[MathIzzzFun]

chrisu:

I read from the other forum that if she start reading from Friday, then I ageed it's 24 days instead of 26.

MathIzzzFun:

[quote=\"chrisu\"]If can selectively choose weekend to read, then why not 525/30 = 17.5. Thus the least no. of days would become 18 days which is not among the mcq answers. I think the answer should be 26days.

Hi

the question aims to mislead students to start on Mon which will give the answer as 26 days.. however, if the reading starts on Fri, we will arrive at the least number of days which is 24 days.

cheers.

[/quote]


Hi

I thought that's what I said in my post ?

...if one assumes that she starts reading on Mon then the answer is 26 - this will be the first and logical approach.. the question requires one to look at the alternate ie starting on Fri....this question is similar to the cube/cuboid cutting type of question - the solution that comes to mind is to fit maximum number of cube/cuboids on each side but usually the solution requires one to look beyond the obvious for eg...

http://i54.tinypic.com/2ykjtbd.jpg\">

cheers.

[chrisu]

I must have misunderstood your point, sorry.

MathIzzzFun:

Hi

I thought that's what I said in my post ?

...if one assumes that she starts reading on Mon then the answer is 26 - this will be the first and logical approach.. the question requires one to look at the alternate ie starting on Fri....this question is similar to the cube/cuboid cutting type of question - the solution that comes to mind is to fit maximum number of cube/cuboids on each side but usually the solution requires one to look beyond the obvious for eg...