Q&A - PSLE Math

[lizawa]

tianzhu:

3) There are 600 children in Team A and 30% of them are boys.
There are 400 children in Team B and 60% of them are boys.
After some children are transferred from Team B to Team A, 40% of the children in Team A and 60% of the children in Team B are boys.
How many children are transferred from Team B to Team A?

This is a tricky one. The key is : The total number of boys before and after the movement is the same.

Total boys = (30% x 600) + (60% x 400) = 420
Total girls = (70% X 600) + (40% x 400) = 580
Total = 1000

After movement, in team A
Boys : Girls
= 4 : 6
= 2 : 3

In team A, there are 5units of children.
In team B, there will be 1000 - 5 units of children.

Team B ratio,
Boys : Girls
= 6 : 4
= 3 : 2
= 3/5(1000 -5u) : 2/5(1000 -5u)


2u of boys in team A + 3/5(1000 - 5u) of boys in team B = 420

2u + 600 - 3u = 420
1u = 180

# of boys in team A after movement = 2u = 360
# of girls in team A after movement = 3u = 540
Total in team A = 900.

# of children transferred from team B to team A = 900 - 600 = 300.

[tianzhu]

lizawa:

Hi Tianzhu,


May I ask which school's paper were these questions from ?

Sorry, lizawa

The person who passed them to me cannot remember the source.Anyway, what is more important is that these questions helped to sharpen our kids' skills in answering Maths questions.Hope fellow members will find them useful.

Best Wishes

[ChiefKiasu]

Looks good! Here's a trial sample of the CDROM:

http://www.misskarey.com/misskarey.htm

I'm ordering one. Will do a review subsequently.

[tianzhu]

Why do parents and pupils have problems with the PSLE Maths paper?


Mr Tan Yap Kwang, chief executive of the Singapore Examinations and Assessment Board (SEAB), offers this explanation: 'For Maths, if you don't understand the question or the concept tested, you cannot even start solving the sum. For English or Mother Tongue, you can always guess an answer.'

What’s your take?

http://www.straitstimes.com/print/Free/Story/STIStory_169062.html
Oct 21, 2007
At sixes and sevens over PSLE Maths

AS FAR as parents and pupils are concerned, PSLE Maths papers often just don't add up.
Howls of outrage greeted this year's test, with mums and dads fuming and some pupils in tears outside the exam room.
Parents also cried foul in 2005, after a flawed question slipped into the paper.
In 2000, about 25 angry parents called The Straits Times to complain about the paper being too difficult.
And in 1992, the Ministry of Education was criticised when parents raged about tough questions.
It all looks like a standard formula: tricky questions plus nervy pupils and expectant parents multiplied by exam pressure equal tears and ill temper.
Why do parents and pupils have problems with the PSLE Maths paper?
Mr Tan Yap Kwang, chief executive of the Singapore Examinations and Assessment Board (SEAB), offers this explanation: 'For Maths, if you don't understand the question or the concept tested, you cannot even start solving the sum. For English or Mother Tongue, you can always guess an answer.'
A maths teacher, who declined to be named, said: 'Maths is the one subject pupils can possibly score 100 marks for, unlike English. So it devastates them when they cannot do well.'
Mr Tan, who feels parents are over-reacting, said this year's paper was no tougher than in other years. 'Sometimes pupils have very high expectations for themselves. Not being able to answer one question is like the end of the world.'
Ten parents and former teachers complained to The Straits Times Forum page that some sums were not in the syllabus.
Mr Tan said the PSLE must differentiate between pupils of different abilities: 'It'd be a problem if 30 per cent of the cohort scores full marks. Then how do you differentiate between the average student and the brightest of the lot?'
Ten teachers told The Sunday Times they had never seen so many pupils crying after a PSLE paper.
One admitted that she needed a calculator to solve one of the sums. Pupils are not allowed to use them.
A teacher was called into the exam hall after a top pupil broke down and wanted to quit. But Mr Norman Tien, a PSLE Maths trainer, said: 'Most students are drilled to do past exam papers. If they come across a question they've never seen before, they'll think it's difficult.'
At least 95 per cent of a cohort should be able to tackle the basic questions, Mr Tan said, while the last few 'challenging' sums are aimed at the brighter ones.
Pupils should not fret if they cannot answer some questions. Mr Tan said: 'You don't need to answer every one correctly to get an A*.'
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[tianzhu]

3) Daniel has $160 more than Alex. After giving 1/10 of his money to Alex, he now has 3 times as much money than Alex. How much money do they have in the first place?



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[KIMC0001]

There were some marbles at a shop. The ratio of the number of red marbles to the number of blue marbles was 2:3. When 50 more red marbles and 30 more blue marbles were added, the ratio of the number of red marbles to the number of blue marbles became 5:6. How many marbles were there at first?


x: red marbles
y:blue marbles

x/y=2/3
(x+50)/(y+30)=5/6

Solving the equation,
3x=2y
6x+300=5y+150-----*

if 3x=2y,(here you times 2 for both side right?)
6x=4y

sub into *
4y+300=5y+150
150=y
y=150

if y=150,
use this formula u have found jus now
3x=2y
3x=2(150)=300
after that,bring 3 over,hence 300 /3=100.
x=100

hence red marbles=100
blue marbles=150

[nicsmom]

Hi KIMC0001,


I do not think a primary school child can understand simultaneous equations or such advance algebra for solving this.

[KIMC0001]

Hi,but my student in primary school can do algebra already:)

[tianzhu]

The answers given in the worksheet are a) 7:1:8 and b) 168.

But, my answer for a) was 7:11:9. You may want to try it out.

(Ai Tong School P6 SA1 Q43 - 2007)
Packets of assorted candies were sold in 2 different sizes - standard and large. The large packet contained twice as many candies as the standard packet. In the standard packet, the ratio of the number of coconut candies to the number of strawberry candies were 4:5. In the large packet, the ratio of the number of coconut candies to the number of strawberry candies to the number of toffee candies was 1: 2: 3.

A family bought 1 standard and 1 large packet.

(a) What was the ratio of the number of coconut candies to the number of strawberry candies to the number of toffee candies?

(b) The family ate 21 candies. As a result, the ratio of the number of coconut candies to the number of strawberry candies to the number of toffee candies became 2: 3: 3. How many candies were left?

[lizawa]

Hi Tianzhu,


Your answer is correct. My son has tried this paper before. But I remembered our answer key did have the correct answer.

Lizawa