Q&A - PSLE Math

[pensiveowl]

Hi jieheng.. I've looked through your soln - thanks for taking the time. I'm wondering about this portion in red. It doesn't seem to be subtracted from the area of the squares ABFE and CDGH. Did I miss something?


http://www.positivelyquit.org/images/arc.jpg\">

[Dharma]

pensiveowl:

I need help with this problem - can someone pls help solve it - thanks


http://www.positivelyquit.org/images/math.jpg\">

http://i54.tinypic.com/2evgeac.jpg\">

[jieheng]

pensiveowl:

Hi jieheng.. I've looked through your soln - thanks for taking the time. I'm wondering about this portion in red. It doesn't seem to be subtracted from the area of the squares ABFE and CDGH. Did I miss something?


http://www.positivelyquit.org/images/arc.jpg\">

http://i52.tinypic.com/wlqeef.jpg\">

Hi pensiveowl ,

Area of un-shaded BEF = Area of un-shaded CHG =Area of square ABFE - area of small quadrant

Area of small quadrant includes Area in Red and Area in Blue

.

[raghupavithra]

i need help for this problem.

1.jennifer was given an end of year bonus. first, she gave half of her bonus plus $40 to her parents.Next, she saved half of her remaining bonus plus $30 in the bank.After that, she donated to charity half of her remaining bonus plus $20.Finally,she spent half of her remaining bonus plus $10 on some clothes.If she was left with $100,how much was her bonus?

2.Lucy wanted to buy a bag that cost $12 but did not have enough money for it.
Alan then agreed to lend her as much money as she had with her.After buying the bag,Lucy wanted to buy a pair of socks that cost$8 but did not have enough money.Randy then agreed to lend her as much money as she had with her.
After buying the pair of socks,Lucy did not have any money left with her.How much money had she at first?

[tianzhu]

Hi


I wish to begin by saying that this is not an easy question on composite figures for twelve years old kids.

As in any questions on “Circles”, it helps if a kid is able to rearrange the figure into familiar shapes.

In this question, you’ll realise that once you separate the medium semi circle(r15) from the initial figure, it becomes easier to see that the area of the shaded areas is equal to area of big semi circle(r24) + area of medium semi circle(r15) + area of small semi circle(r9) – area of rectangle ABCD. The two small quadrants (r9) add up to form a semi circle (r9).

If a kid is able to visualise this, he may skip the step on further breaking down the big semi circle, 2 quadrants and rectangle into smaller parts. Otherwise label the parts as shown in the image as it helps one to see better.

Hope this helps.

Best wishes.

http://farm7.static.flickr.com/6139/5961159714_a582e4ddac_z.jpg\">

[lizawa]

raghupavithra:

i need help for this problem.

1.jennifer was given an end of year bonus. first, she gave half of her bonus plus $40 to her parents.Next, she saved half of her remaining bonus plus $30 in the bank.After that, she donated to charity half of her remaining bonus plus $20.Finally,she spent half of her remaining bonus plus $10 on some clothes.If she was left with $100,how much was her bonus?

http://i55.tinypic.com/2w7fghz.jpg\">

[pensiveowl]

Thanks Dharma, tianzhu and jieheng

[lizawa]

raghupavithra:

i need help for this problem.

2.Lucy wanted to buy a bag that cost $12 but did not have enough money for it.
Alan then agreed to lend her as much money as she had with her.After buying the bag,Lucy wanted to buy a pair of socks that cost$8 but did not have enough money.Randy then agreed to lend her as much money as she had with her.
After buying the pair of socks,Lucy did not have any money left with her.How much money had she at first?

http://i54.tinypic.com/kf5kiw.jpg\">

[bobsg01]

Problem in ratio question.


Thanks for your help in advance.

http://i52.tinypic.com/2dgvp0l.jpg\">

[stary]

bobsg01:

Problem in ratio question.


Thanks for your help in advance.

http://i52.tinypic.com/2dgvp0l.jpg\">

Before -> (John = 3 units) (Sally = 7 units)
After -> (John = 3 parts) (Sally = 2 parts)

1 part -> 76
5 parts -> 5 x 76 = 380
Sally (after) -> 2 x 76 = 152

10 units -> 380
7 units -> 7/10 x 380 = 266

Sally to John -> 266 - 152 = 114 (a)
Percentage -> 114/266 x 100% = 42 6/7% (b)