Q&A - PSLE Math

[Ready2WORK]

Ready2WORK:

paranoid:

http://i49.tinypic.com/2qwcsr9.jpg\">


Question from NHPS Prelim 2012 :imdrowning:

@paranoid,
This is the working. Will attach image later if needed. Correct me if I am wrong.
28+28+14+14=84
28+14=42
1/2*84*42=1764
1/2*22/7*28(squared)=1232
1764-1232=532
532/4=133
1/8*22/7*28(squared)=308
308-133=175
Answer: 175

@paranoid,
Here is the image if needed.
http://i49.tinypic.com/t8uhol.png\">
The blue dots are all the same, and they are the areas, not lengths.
The cm squares are not written. :salute:

[tianzhu]

kay22:

http://i47.tinypic.com/347xpn8.jpg\">

Hi

Let the length (slanting) of one isosceles triangle be 1a.

16a -------- 2y + 112

a --------- y/8 + 7

Perimeter of each isosceles triangle ------- 2(y/8 + 7) + y/4 --------- y/2 + 14

If y=40

Perimeter of each isosceles triangle ------- y/2 + 14 --------- 40/2+ 14 -------- 34

Best wishes

[Ready2WORK]

tianzhu:

kay22:

http://i47.tinypic.com/347xpn8.jpg\">

Hi

Let the length (slanting) of one isosceles triangle be 1a.

16a -------- 2y + 112

a --------- y/8 + 7

Perimeter of each isosceles triangle ------- 2(y/8 + 7) + y/4 --------- y/2 + 14

If y=40

Perimeter of each isosceles triangle ------- y/2 + 14 --------- 40/2+ 14 -------- 34

Best wishes

If the perimeter of each isosceles triangle is 34, then each side must be 11 one-third, so y would then be 11 one third times 4, which is then 45 one-third. Explain? :scratchhead:

[AJH]

tianzhu:

AJH:

[quote=\"tianzhu\"]
But isn't 30% of students in the parade ground and 70% of students at the indoor sports hall = 180 + 280 = 460?

Hi

Good Morning.

The number of boys and girls remains the same before and after the transfer. The total number of 1000 did not change at all.

The number of girls stays the same that is 480 before and after.

In this case

Number of girls in the beginning ------- 480

Number of girls in the end (after the transfer)

Parade square ------- 3 parts ------ 3*55 ------- 165 (30% of 550)

Indoor stadium -------- 7 units ------- 7*45 ------- 315 (70% of 450)

Total number ------ 165 + 315 ------- 480

Best wishes[/quote] :thankyou: for all the help you have given me.

[AJH]

Hi - PSLE Maths is this Friday. I want to thank everyone for your help.

:thankyou: very much for your time and effort. I appreciate what all of you have done.

[Ready2WORK]

AJH:

Hi - PSLE Maths is this Friday. I want to thank everyone for your help.

:thankyou: very much for your time and effort. I appreciate what all of you have done.

Yup! Good luck. For you and me. :celebrate:

[kiasuaunt]

I would also like to join my god-daughter to thank all of you for your kindness and generosity.We have benefitted much from this - you have all made this journey less painful and frustrating. :thankyou: and God Bless.

[paranoid]

tianzhu:

paranoid:

Question from NHPS Prelim 2012

Hi

I’ve not much time for slide now.

Try to rearrange the shaded part.

Area of shaded part ------- Area of quadrant (r28) – area of triangle (1/2*28*28)

Best wishes

Hmm Tianzhu, how can it be proven that the shaded part A can be re-arranged to form a half-rugby like you mentioned? Someone else provided a different answer.

[Ready2WORK]

paranoid:

tianzhu:

[quote=\"paranoid\"]

Question from NHPS Prelim 2012

Hi

I’ve not much time for slide now.

Try to rearrange the shaded part.

Area of shaded part ------- Area of quadrant (r28) – area of triangle (1/2*28*28)

Best wishes

Hmm Tianzhu, how can it be proven that the shaded part A can be re-arranged to form a half-rugby like you mentioned? Someone else provided a different answer.[/quote]I was thinking about that point too, but you can't be sure that it rearranges into a exact half-rugby. So that was probably not the solution.

[tianzhu]

paranoid:

Hmm Tianzhu, how can it be proven that the shaded part A can be re-arranged to form a half-rugby like you mentioned? Someone else provided a different answer.

Hi

When dealing with composite figures, one of the more efficient ways is to work with familiar shapes. Students should be pretty well versed in familiar shapes.

The answer to your question is 224 sq cm.

Hope this helps.

Best wishes

http://farm9.staticflickr.com/8462/8024994319_c3bfa77fea_z.jpg\">