Q&A - PSLE Math

[Neat]

Hi!


Please help!

Alif collected 1400 stamps and 35% of them were Singapore stamps. Fong collected 600 stamps and 55% of them were Singapore stamps. After Alif had given some of his stamps to Fong and Fong had given some of his stamps to Alif, 1/5 of Alif’s stamps and 3/5 of Fong’s stamps were Singapore stamps. How many Singapore stamps did Fong get from Alift?

Thank You.

[speedmaths.012624com]

Neat:

Hi!


Please help!

Alif collected 1400 stamps and 35% of them were Singapore stamps. Fong collected 600 stamps and 55% of them were Singapore stamps. After Alif had given some of his stamps to Fong and Fong had given some of his stamps to Alif, 1/5 of Alif's stamps and 3/5 of Fong's stamps were Singapore stamps. How many Singapore stamps did Fong get from Alift?

Thank You.

Hi,

One possible solution:
Using the Advanced Model Method
(or Bags and Boxes Method)

Alif collected 1400 stamps;
35% (or 490) of them were Singapore stamps
65% (or 910) of them were non-Singapore stamps

Fong collected 600 stamps:
55% (or 330) of them were Singapore stamps
45% (or 270) of them were non-Singapore stamps

Total Singapore stamps → 490 + 330 = 820
Total non-Singapore stamps → 910 + 270 = 1180

After the exchange:
(1/5 of Alif's stamps were Singapore stamps.)
Let Alif put his stamps into 5 Bags
1 Bag of Singapore stamps
4 Bags of non-Singapore stamps

After the exchange:
(3/5 of Fong's stamps were Singapore stamps)
Let Fong put his stamps into 5 Boxes
3 Boxes of Singapore stamps
2 Boxes of non-Singapore stamps

After the exchange:
Singapore stamps: \t\t1 Bag + 3 Boxes → 820
Non-Singapore stamps: \t4 Bags + 2 Boxes → 1180

1 Bag + 3 Boxes → 820
(x 4)
4 Bags + 12 Boxes → 3280\t(Row 1)

4 Bags + 2 Boxes → 1180\t(Row 2)

Row 1 – Row 2
0 Bag + 10 Boxes → 2100

10 Boxes → 2100
1 Box → 210
3 Boxes → 630

After the exchange,
Fong had 630 Singapore stamps
630 – 330 = 300

Fong received 300 Singapore stamps from Alif.

Hope this helps.

Cheers

speedmaths.com

PS.
Parents who wish to know more about the Advanced Model Method can check out our thread in the Happenings forum.

.

[MathIzzzFun]

Neat:

Hi!


Please help!

Alif collected 1400 stamps and 35% of them were Singapore stamps. Fong collected 600 stamps and 55% of them were Singapore stamps. After Alif had given some of his stamps to Fong and Fong had given some of his stamps to Alif, 1/5 of Alif's stamps and 3/5 of Fong's stamps were Singapore stamps. How many Singapore stamps did Fong get from Alift?

Thank You.

http://i49.tinypic.com/6ygwa8.png\">

cheers.

[superksmum]

Hi need help on these 2 questions (extract from SNG 2011 Prelim):


Question 17
A shopkeeper had some markers in red and blue. If 50 red markers and 25 blue markers were sold each week, there would be 500 red markers left when all the blue markers were sold. If 25 red markers and 50 blue markers were sold each week, there would be 800 red markers left when all the blue markers were sold. How many markers did the shopkeeper have at first?

Question 18
A rectangle tank measuring 40cm by 30cm was 1/6 filled with water. At 0930hrs, Tap X with water flowing out at a rate of 3litre per minute was turned on. At 0932hrs, Tap Y was turned on to drained water out of the tank at a fixed rate. At 0943hrs, the tank was 75% filled with water. At what time would the tank be filled to the brim?
(Ans: 0954hrs, however ours is 0949hrs)


Thank you.

[anneshirleygilbert]

MathIzzzFun:

anneshirleygilbert:

Can somebody please help me with this question?


Alan bought 1.5 times as many pencil cases as pens and spent $300 altogether. He spent $60 more on pens than on pencil cases. Given that a pen costs $3.50 more than a pencil case, find the cost of a pencil case.

TIA

Please confirm number in blue.

cheers.

That is indeed $3.50 as it appeared in my daughter's worksheet. Maybe, it's a typo error. I was trying to compare 1u of pencil cases and 1u of pens, but couldn't get a neat whole number. Never mind, will re-post when I get confirmation from my daughter. Thanks though.

[MathIzzzFun]

superksmum:

Hi need help on these 2 questions (extract from SNG 2011 Prelim):


Question 17
A shopkeeper had some markers in red and blue. If 50 red markers and 25 blue markers were sold each week, there would be 500 red markers left when all the blue markers were sold. If 25 red markers and 50 blue markers were sold each week, there would be 800 red markers left when all the blue markers were sold. How many markers did the shopkeeper have at first?

Question 18
A rectangle tank measuring 40cm by 30cm was 1/6 filled with water. At 0930hrs, Tap X with water flowing out at a rate of 3litre per minute was turned on. At 0932hrs, Tap Y was turned on to drained water out of the tank at a fixed rate. At 0943hrs, the tank was 75% filled with water. At what time would the tank be filled to the brim?
(Ans: 0954hrs, however ours is 0949hrs)


Thank you.

both questions were discussed earlier -
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&p=805210&hilit=measuring+40cm+by+30cm#p805210

cheers.

[superksmum]

MathIzzzFun:

superksmum:

Hi need help on these 2 questions (extract from SNG 2011 Prelim):


Question 17
A shopkeeper had some markers in red and blue. If 50 red markers and 25 blue markers were sold each week, there would be 500 red markers left when all the blue markers were sold. If 25 red markers and 50 blue markers were sold each week, there would be 800 red markers left when all the blue markers were sold. How many markers did the shopkeeper have at first?

Question 18
A rectangle tank measuring 40cm by 30cm was 1/6 filled with water. At 0930hrs, Tap X with water flowing out at a rate of 3litre per minute was turned on. At 0932hrs, Tap Y was turned on to drained water out of the tank at a fixed rate. At 0943hrs, the tank was 75% filled with water. At what time would the tank be filled to the brim?
(Ans: 0954hrs, however ours is 0949hrs)


Thank you.

both questions were discussed earlier -
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&p=805210&hilit=measuring+40cm+by+30cm#p805210

cheers.

:thankyou: MathIzzFun.

[jonaandr]

please help to solve this problem sum.


1. Ken and Sam share some marbles. The ratio of the number of marbles Ken has to the number of marbles Sam has is 5:3. If Ken’s marbles increases by 15%, what percentage of Sam’s marbles must be decreased so that the total number of marbles they have remained unchanged?

[speedmaths.012624com]

jonaandr:

please help to solve this problem sum.


1. Ken and Sam share some marbles. The ratio of the number of marbles Ken has to the number of marbles Sam has is 5:3. If Ken's marbles increases by 15%, what percentage of Sam's marbles must be decreased so that the total number of marbles they have remained unchanged?

Hi,

One possible method:
Use PIYO - Put in Your Own (numbers)

Let Ken have 500 marbles.
Let Sam have 300 marbles.
(Total = 800 marbles)

Ken's marbles increased by 0.15 x 500 = 75 marbles.

Sam's marbles must decrease by 75 marbles.

Percentage decrease is 75/300 x 100% = 25%

Hope this helps.

Cheers



speedmaths.com


.

[jonaandr]

speedmaths.com:

jonaandr:

please help to solve this problem sum.


1. Ken and Sam share some marbles. The ratio of the number of marbles Ken has to the number of marbles Sam has is 5:3. If Ken's marbles increases by 15%, what percentage of Sam's marbles must be decreased so that the total number of marbles they have remained unchanged?

Hi,

One possible method:
Use PIYO - Put in Your Own (numbers)

Let Ken have 500 marbles.
Let Sam have 300 marbles.
(Total = 800 marbles)

Ken's marbles increased by 0.15 x 500 = 75 marbles.

Sam's marbles must decrease by 75 marbles.

Percentage decrease is 75/300 x 100% = 25%

Hope this helps.

Cheers



speedmaths.com


.

Thank you very much!!