Q&A - PSLE Math

[tianzhu]

mvmir26:

Please help on below


There are 200 red balls and 90 blue balls in basket A. There are 80 red balls and 100 blue balls in basket B. Find the total number of balls that must be transferred from basket B to basket A so that 60% of the balls in basket A and 50% of the balls in basket B are red balls.

Hi

This question touches on simultaneous concept.

The units showing the number of red balls and the number of blue balls are not of the same kind and measure. They are representing different sets of objects.

You may solve it in three ways.

1)Using Units and Parts to show red and balls.
2)Using letters of the alphabet to show red and blue balls.
3)Solve the equations pictorially.

There are some examples of similar type of questions in previous posts in this thread.

Basket A

Red ----- 3 units
Blue ----- 2 units

Basket B

Red ----- 1 part
Blue -----1 part

3 units + 1 part ------ 200+80 ------- 280 (red)
2 units + 1 part ------ 100+90 ------190 (blue)

1 unit ----- 90
1 part ----- 10

Red balls transferred from B to A -------- 80 -10 ------70
Blue balls transferred from B to A -------- 100 -10 ------90

Total number of balls transferred from B to A ------- 160.

Best wishes

[mvmir26]

Thank you Tianzhu.

[MathIzzzFun]

mvmir26:

Please help on below


There are 200 red balls and 90 blue balls in basket A. There are 80 red balls and 100 blue balls in basket B. Find the total number of balls that must be transferred from basket B to basket A so that 60% of the balls in basket A and 50% of the balls in basket B are red balls.

Hi

a model approach...

http://i55.tinypic.com/2sb75w4.jpg\">

cheers.

[reddotresident]

tianzhu:

Fairy Best Freinds:

Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil, find the cost of a pencil.


Thank you.

Hi

You may use MD for this question.

Sorry no time to draw now, but there are some examples in previous posts.

NB ----- 12
Pencils ----- 9.6

9.6/4 ------ 2.4

12 – 2.4 ----- 9.6

A notebook costs $3.20 more than a pencil.
9.6/3.2 ----- 3

There are 3 NB, therefore 12 pencils.

Cost per pencil ----- 9.6/12 ------ 80 cents.

Best wishes

How did you find out that it is 12 NBs..sorry quite blur, pls help!

[tianzhu]

reddotresident:

How did you find out that it is 12 NBs..sorry quite blur, pls help!

Hi

Cost of NB + pencils -------21.6

NB costs 2.40 more

Therefore, pencils cost $9.6 and NBs cost $12

Best wishes

[marcusya]

HI,

  Citrine bought twice as many pencils as notebooks and spent a total of $53.60. She spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $1.90 more than a pencil, find the cost of a pencil.
The answer is 1.60 but i dont know the steps to solving this sum.
Thanks!

[small]

marcusya:

HI,

  Citrine bought twice as many pencils as notebooks and spent a total of $53.60. She spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $1.90 more than a pencil, find the cost of a pencil.
The answer is 1.60 but i dont know the steps to solving this sum.
Thanks!

Hi,

HTH….

First, find the total cost for pencils as notebooks:
Total cost of pencils = ($53.60-$2.40)/2 = $25.60
total cost of notebooks = $53.60 - $25.60 = $28.00

Citrine bought twice as many pencils as notebooks, which means :
2 units of pencils = $25.60 (1 unit of pencils = $12.80)
1 unit of notebooks = $28.00


Given that a notebook costs $1.90 more than a pencil, so number of notebook in each unit will be ::

(Price of 1 unit of notebooks - Price of 1 unit of pencils ) / 1.90
= ($28.00-$12.80)/$1.90
= $15.20 / $1.90
= 8 (notebooks in a unit)

So there are 16 pencils altogether.
$25.60 / 16 = $1.60

The cost of a pencil is $1.60.

[ASK TalkMaths]

marcusya:

HI,

  Citrine bought twice as many pencils as notebooks and spent a total of $53.60. She spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $1.90 more than a pencil, find the cost of a pencil.
The answer is 1.60 but i dont know the steps to solving this sum.
Thanks!

Hi marcusya,

I have solved your question. The solution is in the following link:
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B81le9JxERBGZWFlNjBlODktNTgzYi00MGY3LWI0MGQtODYyYzRhZmVmOGVj&hl=en_GB

Feel free to clarify with me if you any problems on my facebook page << Mod's Note - URL Removed according to forum's rules >>

[tianzhu]

mvmir26:

Thank you Tianzhu.

Hi

You’re welcome.

Wishing you the very best for PSLE 2011.

Best wishes

[Daddy]

Hi Tianzhu,


http://i56.tinypic.com/zvse95.jpg\">

Did not understand the chicken units is not the same size as ducks and quails? Which part of the question said that they are different. Thanks.

Most question I had asked for whole numbers. The units for different objects is the same size and make them equal to each othe?

I confusion on the chickens, duck and quail quesions. Please help?!! Thanks.