Q&A - PSLE Math

[P.047330KH]

Hi, can anyone please help me solve the following questions. These are from Methodists girls school maths prelims 2010 paper. I know the answers but don’t understand how to derive at that.


1. On the reverse side of a card is a number. The decimal point of this number is shifted to the right twice. The difference between the new number and the initial number is 544.5. What is the number written on the card?

2. John and Sarah collected some cans for their project. John collected 25% more cans than Sarah. Then he gave 20 of his cans to Sarah and she had 20% more cans than him.
a) how many cans did they have in all?
b) how many more cans must John give to Sarah in order for Sarah to have 25% more than him?

[tianzhu]

P.KH:

Methodists girls school maths prelims 2010 paper.

1. On the reverse side of a card is a number. The decimal point of this number is shifted to the right twice. The difference between the new number and the initial number is 544.5. What is the number written on the card?

2. John and Sarah collected some cans for their project. John collected 25% more cans than Sarah. Then he gave 20 of his cans to Sarah and she had 20% more cans than him.
a) how many cans did they have in all?
b) how many more cans must John give to Sarah in order for Sarah to have 25% more than him?

Hi

Good Morning.

When the decimal point of a number is shifted to the right twice, it means that the original number is multiply by 100.

For example , 5.8 becomes 580.

You may use MD or UM.

Hence, initial number ------1 unit
New number ------ 100 units

Difference ------99 units ---------544.5

1 unit --------5.5


For Q2.the number of cans remains the same before and after.

(a)

At first.
John: Sarah
5:4
55:44

In the end.
John: Sarah
5:6
45:54

10 units ------ 20
1 unit -----2

99 units -----198.

(b)

20% ------- 10 cans
5% --------2 cans

John must give to Sarah 2 more cans

Best wishes

[tianzhu]

pensiveowl:

Ok thanks very much again..

Hi

Good Morning.

You're welcome.

Best wishes

[tianzhu]

mumwgals:

Thank you so much, tainzhu! Your explaination is brilliant!! :thankyou:

Hi

Good Morning.

You're welcome.

Best wishes

[tianzhu]

jeysri72:

Q17:there were 1000 students at the parade ground and indoor sports hall. 40% of the 600 students at the parade ground were girls. 60% of the students at the indoor sports hall were girls. After some of the students in both venues moved from one venue to the other, 30% of the students in the parade ground and 70% of the students at the indoor sports hall were girls. How many students were there in the indoor sports hall after the movement had taken place? Ans: 450

Hi

Good Morning.

This question was first discussed on page 434.
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=4330

http://farm7.static.flickr.com/6070/6154555481_a1f43e1359_z.jpg\">

[tianzhu]

jeysri72:

Q18: A large warehouse had a total of 2180 black, red and white t-shirts for sale. the ratio of black t shirt to red t shirts was 3:1. after 2/5 of the black t shirts and 1/3 of the white t shirts and none of the red t shirts were sold, there were 1504 t shirts left. how many red t shirts were there at first? ans: 380

Hi

You may use MD or UM.

At first
Black ---- 15 units (3)
Red -----5 units (1)
White ---- 3 parts

Sold

Black ------ 6 units
Red ----- none
White -----1 part

Left
Black ------ 9 units
Red ----- 5 units
White -----2 parts

9 units + 5 units + 2 parts ----- 1504

14 units + 2 parts ------1504 ----------( E1)

20 units + 3 parts ------2180 -------- (E2)

(E2) –(E1) gives 6 units + 1 part ------676

From (E1)

2 units + 2(676) --------1504

1 unit -----76

At first, red t shirt --- 5 units -----5*76 -------380

Best wishes

[ck123]

Hi

Can someone confirm the answer for nan hua 2011 prelim maths paper 2 question 14? Answer given 34 seats my answer 39 seats if I am wrong please help to show the workings thanks.

[P.047330KH]

Dear tianzhu , thanks a lot for your quick reply … It was really helpful . 

[Vanilla Cake]

ck123:

Hi

Can someone confirm the answer for nan hua 2011 prelim maths paper 2 question 14? Answer given 34 seats my answer 39 seats if I am wrong please help to show the workings thanks.

For the benefit of interested readers who have no access to Nan Hua 2011 P6 Prelim Maths exam paper, here's the paper 2 Q14 while waiting reply from KSP members to confirm the correct answer:

A train has a capacity of 154 seats. Tickets for seats are sold at $8 and $12. There are 1/5 more $8-seats than $12-seats on the train. During a trip, the amount collected from the sales of $8 tickets was twice the amount collected from the $12 tickets. The total amount collected was $540. How many $8-seats were not taken during the trip?

VC's mum

[andante]

ck123:

Hi

Can someone confirm the answer for nan hua 2011 prelim maths paper 2 question 14? Answer given 34 seats my answer 39 seats if I am wrong please help to show the workings thanks.

Hi,
The answer given for my nan hua paper is 39 and my DD also worked out as 39.