Q&A - PSLE Math

[tianzhu]

Tang:

1 Adult unit --> 21 - 2 x 18 = 5 parts

So 1 Child unit --> 8 - 5 = 3 parts

Child / Total = 3/(3+5) = 3/8

Hi Tang

How do you get (2X18)?

[Tang]

tianzhu:

Tang:

1 Adult unit --> 21 - 2 x 18 = 5 parts

So 1 Child unit --> 8 - 5 = 3 parts

Child / Total = 3/(3+5) = 3/8

Hi Tang

How do you get (2X18)?

Sorry Uncle Tianzhu,

There is a typo error. It should be 8 and not 18.

1 Adult unit --> 21 - 2 x 8 = 5 parts

I have amended the post.

[Dharma]

tianzhu:

Hi Dharma


I am wondering why you used units and parts for the number of people. For the number of adults and children, we are using the same measures to indicate the ratio representing the number of adults to the number of children. Likewise for the price of tickets, we are using the same units of measurement to represent the dollar values of the tickets.

How do you arrive at 1p/ (1u+1p) = 3/8?

This is not an easy question as students have to have clear understanding of the differences between the units representing quantity and those representing the dollars values.

Please help to explain.

Sorry bro,

Used units and parts to represent ratio of adults to children but we were not given that info.

The ticket price/fare and costs of tickets – insert $ to show that it has dollar value.

But ratio of 8/21 … the denominator is actually the number of dollars of the tickets (So NO $ sign reqd)

1u + 1p = Total no. of tourist

1u + 1p/ (3u + 2p) = 8/21
Cross multiplying
3u = 5p

1p/1u = 3/5 (Child : Adult ratio = 3:5)

Therefore; child : tourist ratio = 3: 8
Fraction of tourist who were children = 3/8




http://www.postimage.org/

[James Ang]

Practise more speed and circle questions this year.



Car A left Town X for Town Y at the same time when Car B left Town Y for Town X. The average speed of Car A was 56 km/h and the average speed for Car B was 72 km/h. The two cars passed each other at a point 24km from the midway of the two towns. What is the distance between Town X and Town Y?

[tianzhu]

Thank you for your help.


http://www.wendykoh.com/08/primary6-swastikasa2-maths.pdf

For Q47, what is your answer for Q47(c)?What is the relationship between the numbers?

[Dharma]

tianzhu:

Thank you for your help.


http://www.wendykoh.com/08/primary6-swastikasa2-maths.pdf

For Q47, what is your answer for Q47(c)?What is the relationship between the numbers?

Hi Tianzhu,

Hope this helps

c)

Pattern 1 = 5 or [5 x 1]
Pattern 2 = 12 = 5 + 7 or [6 x 2]
Pattern 3 = 21 = 5 + 7 + 9 or [7 x 3]
Pattern 4 = 32 = 5 + 7 + 9 + 11 or [8 x 4]
.
.

Pattern N = (N+ 4) x N = 285

Use Guess and check
19 x 15 = 285 (Pattern 15)

[suiyuan]

Please help.Thank you.


There are 2200 students in a primary school. Each student attends 10 classes during the day. Each class has 40 students and 1 teacher. During the day, each teacher teaches 10 classes. What is the smallest number of teachers the school can have?

[ApronMama]

Dear parents, my child taking PSLE in 2010 (next year). May I know whether the Maths papers format are the same as this year (2009)? Also, for long questions (The last 13 questions when calculator can be used, correct me if I am wrong) whether units a must to carry along with the steps of the soluntion ? I asked because last year P6 told me units need not carry along, but only required to write once at the final answer…


Appreciate your clarification.

[faith2u]

1). In a class, there are 4 more boys than girls. 1/3 of the girls and 7/11 of the boys take the MRT train to school. If ½ of the class take the MRT, how many boys and girls are there in the class?


2). The ratio of the number of 50cent coins to the number of 10cent coins in a box was 5:3. 5-50cent coins were taken out and exchanged for 10cent coins of equal value. The money was then put back into the box. The ratio of 50cent coins to 10cent coins became 1:2.
(a). how much money was there in the box?
(b). if 10 10cent coins were taken out and exchanged for 20cent coins and the money returned to the box, what would the ratio of the number of 10centcoins to the number of 20cent coins to the number of 50cent coins be then? Give your answer in the simplest form.

Thanks.

[James Ang]

James Ang:

Practise more speed and circle questions this year.



Car A left Town X for Town Y at the same time when Car B left Town Y for Town X. The average speed of Car A was 56 km/h and the average speed for Car B was 72 km/h. The two cars passed each other at a point 24km from the midway of the two towns. What is the distance between Town X and Town Y?

2 more speed questions;

1) A car travels from Town X to Town Y at a constant speed. If the car increases its speed by 20%, it will reach Town Y one hour earlier. If the car increases its speed by 25% after travelling for 120 km, it will reach Town Y 48 minutes earlier. Find the distance between Town X and Town Y.

2) Andy and Ben started travelling at the same time from Town X and reached Town Y at the same time. During the journey, Andy spent 1/3 of Ben's travelling time resting while Ben spent 1/4 of Andy's travelling time resting. Find the ratio of Andy's speed to Ben's speed.