Q&A - PSLE Math
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ozora:
Need some pointers on the following questions using units methods
a) There were black and white balls in a bag.
If 20 black balls are removed from the bag, the total number of balls left will be 7 times the number of black balls left.
If 50 white balls are removed from from the bag, the total number of balls left will be 5 times the number of black balls left.
How many balls are there in the bag?
thanks
Total number of white balls : black balls --> 6 units : 1 unit + 20
If 50 white balls are removed:
Number of white balls : black balls --> 4 x ( 1 units + 20) : 1 unit + 20
total white balls:
6 units = 4 units + 80 + 50
1 unit --> 65
Total number of balls --> 7 x 65 + 20 = 475
cheers. -
ozora:
similar questions here :Need some pointers on the following questions using units methods
b) Box A contains 350 black balls and 500 white balls.
Box B contains 400 black balls and 100 white balls.
How many black and white balls must be removed from Box B to Box A in order to have 50% of marbles in A are black and 75% of the marbles in B are black.
thanks
- http://www.flickr.com/photos/62167097@N02/7080366811/in/set-72157629537287046
- http://www.flickr.com/photos/62167097@N02/6858744276/in/set-72157629537287046
Total, black balls → 750
Total, white balls → 600
Total, black and white balls → 1350
In the end:
Total, black balls : ½ Box A + ¾ Box B →750
Total, white balls: ½ Box A + ¼ Box B → 600
½ Box B → 750 – 600 = 150
Box B → 300
Box A → 1350 – 300 = 1050
Balls moved from Box B to Box A :
Black balls → 400 – ¾ x 300 = 175
White balls → 100 – ¼ x 300 = 25
cheers. -
MathIzzzFun:
this is definite clearer to understand. I got stuck trying to use the methods provided by the previous examples.
similar questions here :ozora:
Need some pointers on the following questions using units methods
b) Box A contains 350 black balls and 500 white balls.
Box B contains 400 black balls and 100 white balls.
How many black and white balls must be removed from Box B to Box A in order to have 50% of marbles in A are black and 75% of the marbles in B are black.
thanks
- http://www.flickr.com/photos/62167097@N02/7080366811/in/set-72157629537287046
- http://www.flickr.com/photos/62167097@N02/6858744276/in/set-72157629537287046
Total, black balls → 750
Total, white balls → 600
Total, black and white balls → 1350
In the end:
Total, black balls : ½ Box A + ¾ Box B →750
Total, white balls: ½ Box A + ¼ Box B → 600
½ Box B → 750 – 600 = 150
Box B → 300
Box A → 1350 – 300 = 1050
Balls moved from Box B to Box A :
Black balls → 400 – ¾ x 300 = 175
White balls → 100 – ¼ x 300 = 25
cheers.
after trf:
Black : white
Box A -> 1triangle: 1 triangle
Box B-> 3 diamonds: 1 diamond.
I do not know how to equate and divide by how many. so how do i go about doing that
as for Q1: i got it and redraw it as below.![](\"http://i50.tinypic.com/tagcg7.jpg\")
http://i50.tinypic.com/tagcg7.jpg\">
-
ozora:
Using units and parts :
this is definite clearer to understand. I got stuck trying to use the methods provided by the previous examples.MathIzzzFun:
Need some pointers on the following questions using units methods
b) Box A contains 350 black balls and 500 white balls.
Box B contains 400 black balls and 100 white balls.
How many black and white balls must be removed from Box B to Box A in order to have 50% of marbles in A are black and 75% of the marbles in B are black.
similar questions here :
- http://www.flickr.com/photos/62167097@N02/7080366811/in/set-72157629537287046
- http://www.flickr.com/photos/62167097@N02/6858744276/in/set-72157629537287046
Total, black balls → 750
Total, white balls → 600
Total, black and white balls → 1350
In the end:
Total, black balls : ½ Box A + ¾ Box B →750
Total, white balls: ½ Box A + ¼ Box B → 600
½ Box B → 750 – 600 = 150
Box B → 300
Box A → 1350 – 300 = 1050
Balls moved from Box B to Box A :
Black balls → 400 – ¾ x 300 = 175
White balls → 100 – ¼ x 300 = 25
cheers.
after trf:
Black : white
Box A -> 1triangle: 1 triangle
Box B-> 3 diamonds: 1 diamond.
I do not know how to equate and divide by how many. so how do i go about doing that
as for Q1: i got it and redraw it as below.
Total, black balls → 750
Total, white balls → 600
Total, black and white balls → 1350
IN the end,
Black balls : White Balls, in Box A --> 1u : 1u (1 triangle : 1 triangle)
Black balls : White Balls, in Box B --> 3p : 1p (3 diamonds : 1 diamond)
Total black balls: 1u + 3p = 750
Total white balls: 1u +1p = 600
So, 2p --> 750 - 600 = 150
1p --> 75
1u --> 600 - 75 = 525
Number of balls moved from B to A:
Black --> 400 - 3 x 75 = 175
White --> 100 - 75 = 25
cheers. -
ozora:
The units approach was used in the posted solution as this method could be understood by P4 students. The solution can be directly translated into a MD solution replacing the units with model blocks.
as for Q1: i got it and redraw it as below.
Here's a solution using the units-parts or UP approach:![](\"http://i48.tinypic.com/3148efb.png\")
cheers. -
MathIzzzFun:
great thanks to u.
The units approach was used in the posted solution as this method could be understood by P4 students. The solution can be directly translated into a MD solution replacing the units with model blocks.ozora:
as for Q1: i got it and redraw it as below.
Here's a solution using the units-parts or UP approach:
cheers. -
Need some guide again in the following question.
John had some money. He spent it all in 3 stores. In each store, he spent $2 more than half of what he had when he entered.
a(how much did he spend at the last store?
b)how much did he have at first -
ozora:
Need some guide again in the following question.
John had some money. He spent it all in 3 stores. In each store, he spent $2 more than half of what he had when he entered.
a(how much did he spend at the last store?
b)how much did he have at first
Total amount at first ---> 8 units
At 1st store, spent --> 4 units + $2, Left --> 4 units - $2
At 2nd store, spent --> 2 units - $1 + $2 = 2 units + $1, Left --> 2units - $3
At 3rd store, spent --> 1 unit -$1.5 + $2 = 1 unit + $0.5
At 3rd store, he spent all that he had left, so
2 units - $3 = 1unit + $0.5
1 unit --> $3.5
at 3rd store, he spent --> $4
total amount he had --> $28
cheers. -
Hi, could any of you Math Guru help me with this p6 math question please:
It takes Eleanor 8 hours to make a quilt by herself. If Kelly helps her, they will take 3 hours to make the quilt. How long would Kelly have taken if she makes the quilt by herself? Express your answer in hours and minutes.
Thanks a lot! -
Oracle:
Total amount of work to make the quilt --> 24 units (LCM of 3 &Hi, could any of you Math Guru help me with this p6 math question please:
It takes Eleanor 8 hours to make a quilt by herself. If Kelly helps her, they will take 3 hours to make the quilt. How long would Kelly have taken if she makes the quilt by herself? Express your answer in hours and minutes.
Thanks a lot!
Eleanir work rate --> 24 units/8h = 3 units /h
Eleanor & Kelly work rate --> 24 units /3h = 8 units/h
Kelly work rate --> 5 units/h
time taken by Kellt alone -> 24/5 h = 4. 8h = 4h 48min
cheers.
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