Q&A - PSLE Math
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tianzhu:
Hipensiveowl:
Hi.. could someone pls help ans this question - thanks
Mr Lim had some red and green beads. 60% of his beads were red and the rest were green. He lost some of his red beads and the percentage of the beads which were red decreased by 40%. He then had 760 red and green beads left. How many red beads did he lose?
(1) 190
(2) 240
(3) 285
(4) 360
I believe you just want to double check the answer to this MCQ.
It is 240.
Best wishes
Yes this is the given ans tianzhu - I posted the question hoping to find out how to do it though -
tianzhu:
Hismileplease:
Colin had $80 more than Donovan at first. After Colin spent 75% of his money and Donovan spent 40% of his money, Donovan had $50 more than Colin. How much money did Colin have at first?
You may use UM or MD to solve it.
I use 20units instead of 10units for the common bar (Colin and Donovan) because I want to avoid working with decimals.
At first.
Colin -------- 20 units + 80
Colin ------- 20 units
In the end
Colin ------- 5 units + 20
Donovan ------ 12 units
Donovan had $50 more than Colin.
12 units ------ 5 units + 20 + 50
1 unit ------- 10
Colin ------20*10 -------200 at first.
Best wishes
The answer given by the teacher is 280. I just simply do not understand teacher's working. -
smileplease:
Hi
The answer given by the teacher is 280. I just simply do not understand teacher's working.
I am sorry to mix up the names.
Colin ------(20*10) + 80 -------280 at first.
I'll revise the solution.
Best wishes -
smileplease:
Hitianzhu:
[quote=\"smileplease\"]
Colin had $80 more than Donovan at first. After Colin spent 75% of his money and Donovan spent 40% of his money, Donovan had $50 more than Colin. How much money did Colin have at first?
You may use UM or MD to solve it.
I use 20units instead of 10units for the common bar (Colin and Donovan) because I want to avoid working with decimals.
At first.
Colin -------- 20 units + 80
Colin ------- 20 units
In the end
Colin ------- 5 units + 20
Donovan ------ 12 units
Donovan had $50 more than Colin.
12 units ------ 5 units + 20 + 50
1 unit ------- 10
Colin ------20*10 -------200 at first.
Best wishes
The answer given by the teacher is 280. I just simply do not understand teacher's working.[/quote]hi
answer is 280..if you follow tianzhu's workings, you will get 280 ... Colin had 20 * 10 + 80 = 280.
cheers. -
pensiveowl:
Hitianzhu:
[quote=\"pensiveowl\"]Hi.. could someone pls help ans this question - thanks
Mr Lim had some red and green beads. 60% of his beads were red and the rest were green. He lost some of his red beads and the percentage of the beads which were red decreased by 40%. He then had 760 red and green beads left. How many red beads did he lose?
(1) 190
(2) 240
(3) 285
(4) 360
I believe you just want to double check the answer to this MCQ.
It is 240.
Best wishes
Yes this is the given ans tianzhu - I posted the question hoping to find out how to do it though[/quote]hi
Blue beads as % of initial total = 40%
Red beads left as % of initial total = 60% x 60% = 36%
% left = 76% of initial total = 760, so 1% = 10
Red beads lost = 40% x 60 % = 24% = 24 x 10 = 240 beads.
cheers. -
pensiveowl:
Hi
Yes this is the given ans tianzhu - I posted the question hoping to find out how to do it though
Red ----- 6 units
Green ----- 4 units
Decreased by 40%
Red -------- 6/10 *6 ------3.6 units
3.6 + 4 ------7.6
7.6 units -------760
1 unit ------100
In the end, red ------360
Therefore lose 600-360----240
Best wishes -
Hi,
Can anyone give a clear explanation on how to solve the problem in RGS Prelim Maths 2011 Paper 2 Question 18?
The question is: Beaker A and Beaker B contain some water. If 46.5 ml of water is drained out from Beaker A, the volume of the water in beaker A will be 60% that of the water in Beaker B. If 32.5 ml of water is drained out from Beaker B will be 85% that of the water in Beaker A. What is the total volume of water in Beaker A and Beaker B?
Ans:290.5 ml -
tianzhu:
Hipensiveowl:
Yes this is the given ans tianzhu - I posted the question hoping to find out how to do it though
Red ----- 6 units
Green ----- 4 units
Decreased by 40%
Red -------- 6/10 *6 ------3.6 units
3.6 + 4 ------7.6
7.6 units -------760
1 unit ------100
In the end, red ------360
Therefore lose 600-360----240
Best wishes
Ok thanks very much again.. -
Can anyone give an explanation and solution for henry park 2011 prelim maths.
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
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 -
Thank you so much, tainzhu! Your explaination is brilliant!! :thankyou:
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