## Tuesday, October 21, 2008

### Singapore Math 5

More questions from EPH P5 Challenging Math courtesy of Monica. Answer and working okay?

1) There were some red, blue and green jelly beans in a bag. The number of red jelly beans was 2 1/3 times the number of green jelly beans. The number of blue jelly beans was 0.5 times the total number of red and green jelly beans. When 200 jelly beans were added into the box, the number of green beans became 1.5 times the original number of green jelly beans, the number of red jelly beans was increased by 1/7 and the number of blue beans was increased by 50. Find the total number of jelly beans in the bag in the end.

2) 2/3 of the number of shells Sheba collected is equal to 3/8 of the number of shells Ann and Dick collected together. Ann collected 1/3 as many shells as Dick.
a) What percentage of the total shells did Ann collect?
b) Express the number of shells Dick collected as a percentage of the number of shells Sheba collected, correct to 2 decimal places.
c) If Dick collected 72 shells more than Sheba, how many shells did the 3 children collect in all?

monlim said...

Very good! Q1 is perfect, model and answer. Q2, part b) and c) correct. Part a) wrong because of careless mistake lah... it's 4/25 not 9/25!! Answer is 16%. See, mummies also make careless mistakes!!

I would draw the portion for Ann and Dick as one portion instead of 2, but I think yours shd be acceptable as well.

Lilian said...

Alamak! Can't believe I made careless mistake, must find a way to keep Brian from seeing this :)

Why don't you show how you would have drawn this; was there any of the nifty slicing towards a different direction that you did in a couple of the earlier questions?

monlim said...

Nah, I would have cut all vertically too, cos this one would have been too complicated to cut horizontally (would have resulted in too many mini parts, difficult to count). So would have drawn like you, only Ann and Dick in one row (to do in 2 rows, you need to calculate before hand how many portions is 1/3. I would calculate after, so cannot draw separately at first).

monlim said...

Isn't it funny that it's the mummies who're doing the sums????

No jet lag ah? Want some more? Must find harder ones, you're getting good!!

Anonymous said...

Many maths competitions are organised throughout the year. The next one coming up is the American Maths Contest 8. Many students (P5 & 6s) take part in these maths olympiads to win awards, so as to increase their chances during DSA period for admission to sec schools.

AMC is organised by maths oasis (google it)

MD

Lilian said...

Thanks MD. I realise Singapore kids take part in all sorts of competitions; I should probably be more proactive but the school we're in now is not exactly supportive of such pursuits. The principal once said (patronisingly I thought) that education/schooling isn't a race...riiiiight...

Lilian said...

Yes more please Mon, but not too hard, later I get discouraged :)

Jet-lagged but no choice, loads of things to do. Forced myself to wake up at 730am (330am Moscow time) cos of Sean's eye check-up. Looks like a further increase in degree despite being on atropine therapy :(

monlim said...

Here are 2 more. If you can do these without problems, then you can graduate from Model School liao!

From CASCO Challenging Maths p4:

1) Jack and Ali are given a certain number of maths problems to solve. If Jack solves 3 problems and Ali solves 1 problem every minute, Jack will have 12 problems unsolved when Ali has finished solving all his problems. If Jack solves 1 problem and Ali solves 2 problems every minute, Jack will have 42 problems unsolved when Ali has finished solving all his problems.
a) How many problems were given to Ali?
b) To finish solving the problems at the same time as Ali, how many problems must Jack solve every minute if Ali solves 4 problems every minute?

2)There are 500 male and 200 female employees in Company A. There are 400 male and 600 female employees in Company B. Some employees are transferred from Company A to Company B. After the transfer, the number of male employees is the same as the number of female employees in Company B and the number of male employees is twice the number of female employees in Company A. How many female employees were transferred from Company A to Company B?

Anonymous said...

Ah..but once your son gets into the sec school that he wants through DSA (Direct School Admission), then there is not so much pressure for PSLE. A score good enough for Express stream (which is about 188 - 200 aggregate) will suffice.

The pressure, hehe, is getting above 265 (that was the cut-off last year) to qualify for the Edusave scholarship worth \$14,400!

Lilian said...

Okay Mon: You're pitching this too high, looks hard, will try when I get home later this evening.

MD: You have to be Singaporean in the first place to qualify for Edusave right? 265??! Siao lah...Everything is so darn competitive in Sg :(

monlim said...

No lah, this is from p4 book leh! Looks hard only, actually not so hard. I have faith in your abilities :)

Anonymous said...

Ya, Edusave scholarships only for singaporeans.

Competitive in Sg? - yup, all the way to A Levels. Did you read about the more than 60+ students from RJC who got perfect score for last year A levels? Many of them did more, such as projects, charity work, CCA, etc, so as to win the coveted scholarships, because having a perfect score just won't do anymore.

MD

Lilian said...

Okay MD, now I'm depressed!

Hopefully future employers become more enlightened and will eschew these so-called "perfect" students and go for the slacker-types who do what their hearts tell them to, not just cause it'll look good on their CVs. He he I'm so evil!

Aiyah not that that will ever happenlah, just wishful thinking on my part!

Lilian said...

Monica: Is the answer for No2 100? Even it it is, I'm a failed Model Student; cos I solved it in a really dumb way.

I can't do No1 at all, there's something blocking me mentally, like I said, I can't see it...Could you guide me by showing me how your 3 tips for models help with this question? What I mean is, imagine if L-A can't do these two questions, how would you help her by not showing her the solution, but prodding her the right direction, how do your 3 tips help? I'm totally lost, arrggggghhhhh!!!

monlim said...

Yes, answer to Q2 is 100. Answer to Q1a is 12, 1b is 16.

Don't worry too much about it, when I first started, I could never solve these "transference" type problems either. In fact, neither I nor L-A could solve these 2 problems last year (when she was in p4). Only when I tried again this year, I could do it (and Q1 definitely took a while!)
L-A could only do Q1 with some guidance, will post a step-by-step tomorrow.

Lilian said...

Thanks Mon for your reassuring words...sigh...

My brain is totally shutting down on me, I think it's going on strike from all the hard work I've been putting it through this past week! So I will wait till tomorrow to see your solution, and go zzzzzzz-ing now.