Q&A - PSLE Math

[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!!

[aps]

Hi


Please help to solve this question:

Yanling had 60 % more stamps than Lena. Tricia had 75% fewer stamps tha Yanling. Yanling and Lena gave Tricia some stamps in the ratio 4:1. As a result, Tricia had 2 and a half times as many stamps as before and Yanling had 300 stamps more than Lena in the end. How many stamps did Lena give to Tricia?

Thanks!

[Neat]

[quote]Thank you, MathsIzzzFun[/quote] :thankyou:

[superksmum]

Pls help:


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 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?

Thank you.

[Neat]

[quote]Hi! Thanks speedmaths.com for solving the problem and the introduction of advanced model method. [/quote]

[superksmum]

Sorry another 2 questions:


1) A glass bottle filled with 6 identical ball bearings weighs 1.05kg. The same bottle when filled with 8 marbles weighs 830g. The mass of each ball-bearing is five times the mass of each marble. What is the mass of the empty glass?

2) John donated 1/4 of his cards and Joseph donated 2/3 of his cards. They have the same number of cards left. What is the ratio of the number of cards John has to the number of cards Joseph has at first?

Thank you.