htn:

Hi, please help for the followings:


1) It takes one day for one man to dig a 2m X 2m X 2m hole. How long does it take 3 men working at the same rate to dig a 4m X 4m X 4m hole?

Hi htn
For this kinda questions, the idea is to apply ratio&proportion systematically.
1 man dig 2m X 2m X 2m hole in one day
1 man dig 4m X 4m X 4m hole in 8 days (becuz (4*4*4)/(2*2*2)=8, direct proportion since u take more time to do more work)
3 man dig 4m X 4m X 4m hole in 8/3 days (more manpower work faster!)

htn:

2) Three students who did not do well in a Social Studies test had to sit for a re-test. below shows their test and re-test marks.

Jeff Test marks 24/60 re-test marks 32/40
Freddy Test marks 30/60 re-test marks 36/40
Karen Test marks 18/60 re-test marks 36/40

a) who improved the most and by what percentage?
b) if the teacher gave each student a final grade using 70% of the test mark and 30% of the re-test mark, what would the final mark of each student be? who had the best result?
TIA

The key to doing (a) & (b) is to understand that performance on a test should be seen as a proper fraction where 1 means full marks and 1/2 means u got half of all the available marks, rather than being misled by the raw absolute scores.
So like 24/60 means ur performance is 2/5.

(a)
The \"hard\" part is probably because the denominator are different.
So in order to compare, we need to make the denominator the same.
step #1 : Simplify all 6 fractions and find a common denominator!
Jeff 24/60 = 2/5 vs 32/40 = 4/5
Freddy 30/60 = 1/2 =5/10 vs 36/40 = 9/10
Karen 18/60 = 3/10 vs 36/40 = 9/10

step #2 : Find the percentage improvement by comparing the numerators for each student individually.
(4-2)/2 = 100%
(9-5)/5 = 80%
(9-3)/3 = 200%

So Karen improved the most, by 200%!

(b) On hindsight, its better to convert the fractions in (a) to upon 100 instead.
Jeff 24/60 = 40/100 vs 32/40 = 80/100
Freddy 30/60 = 1/2 =50/100 vs 36/40 = 90/100
Karen 18/60 = 30/100 vs 36/40 = 90/100

final scores (out of 100)
Jeff : 70% * 40 + 30% * 80 = 28 + 24 = 52
Freddy : 70% * 50 + 30% * 90 =35 + 27 = 62
Karen : 70% * 30 + 30% * 90 =21 + 27 = 48
hence Freddy as the best grade!

So now u roughly know how your grade in school is computed!

HAPPYH:

Hi all,


Any suggestions to teach perpendicular lines that comes in a more complex format? Thanks in advance

any concrete examples?

Teacher Aaron:

regularly consult your lecturers and tutors

What he said is especially true... if i am not wrong poly is similar to uni, (since tertiary institution) in that your \"teachers\" won't chase after u to ensure u do your work etc (unlike in sec sch/jc/pri sch). One really has to have the self-discipline to go consult your lecturers and tutors regularly to clear up your doubts.

Jamesbond:

http://i62.tinypic.com/keeoep.jpg\">

Pl help.

The pattern here seems a bit strange but i shall interpret that the first column is an \"anormaly\" and that the pattern occurs every 3 rows.

One technique to solving such problems is to spot where patterns of numbers is contained in which row.
for example notice that multiples of 8 are in column N
and multiples of 8 + 1 are in column L.

So we find 455 with regard to multiples of 8.
455 = 456-1=57*8 - 1

And based on the table multiples of 8 - 1 are in column M!

hence the ans is M.

Jamesbond:

http://i57.tinypic.com/1zc2vr4.jpg\">

Pl help.

Since the two triangles are identical, the three angles are really a, b and c. Hence to find b+c, can start by finding a.

Staring at the left protuding part which contains angle a, using vertically opposite and exterior angle u can get a = 96 - 58 = 42.
hence b+c = 180-a = 138

iggy:

Wesim:

Yep, we are fully aware that this issue might arise. We will see how it goes when my dd enters P1 next year:)

You are right, maybe she likes reinforcing her learning... 温故知新

omg nice chengyu!

biggirl:

How do i score well in poly? To get into local uni/.

My impression of poly is that there will always be projects which form a substantial components of your grade for each module... so pray that u get good teammates!

Kmumz:

Hi all,


I have had the same experience. I bought some science kits on simple machines and they did not work. I heard about this place that develops science 'toys' based on primary school concepts. They teach you how to make your own science toys and you can do it using things from home. They also have huge bubble solutions which really thrilled my kids and they teach you how to explain to your kids about the concept behind the bubbles. Let me know if you need the contact.

whoaa ... which place!?

slmkhoo:

starlight1968sg:

[quote=\"slmkhoo\"]Econs is more 'maths-science' and less 'humanities' than Geog or Hist, so science students usually think it will be easier to understand and study. Most science students also think that Geog/Hist are purely memorising subjects (I disagree, but that's another topic), and prefer not to try them. Another constraint is how each JC timetables classes - not all combinations may be possible.

My thinking is since the student will be doing Geo or Hist in sec 3 & 4, perhaps it is better to continue further (to A levels) rather than to take up Economics from ground zero?

Econs is a very useful subject though, especially if your child wants to do any finance, business etc courses. It's also a good course just for general knowledge. But the main thing is to let your child decide based on interest. Studying needs motivation, and it will be easier if she is interested in the subject.[/quote]Agreed, econs is interesting just for the general knowledge

BitterSweet:

hello, would just like to check something - if I have passed higher chinese in o levels and choose to be exempted from H1CL in A levels, what would it say on my A level cert? would it show my o level higher chinese grade or would it just say that I am exempted?

I think it just won't show up in your A level cert.