Q&A - PSLE Math

[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\">

[zanen]

someone help with me my hw pls Andy sold thrice as many $5 T-shirts as $10 T-shirts. He also sold twice as many $10 T-shirts as $20 T-shirts. He collected $160 more from selling $5 T-shirts than from selling $20 T-shirts.

[excelhub]

zanen:

someone help with me my hw pls Andy sold thrice as many $5 T-shirts as $10 T-shirts. He also sold twice as many $10 T-shirts as $20 T-shirts. He collected $160 more from selling $5 T-shirts than from selling $20 T-shirts.

every $15 (3* $5), he will have $10 (1*$10)

every $20 (2 * $10 ), he will sell $20 (1*$20).

hence,

every 1 set : 6 ($5), he will have 2 ($10) & 1 ($20).

total, $160/10, 16 sets.

[zanen]

excelhub:

zanen:

someone help with me my hw pls Andy sold thrice as many $5 T-shirts as $10 T-shirts. He also sold twice as many $10 T-shirts as $20 T-shirts. He collected $160 more from selling $5 T-shirts than from selling $20 T-shirts.

every $15 (3* $5), he will have $10 (1*$10)

every $20 (2 * $10 ), he will sell $20 (1*$20).

hence,

every 1 set : 6 ($5), he will have 2 ($10) & 1 ($20).

total, $160/10, 16 sets.

thankyou you know this qns too? Tom and Jerry each has some money. If Tom spends $9 per day and Jerry spends $3 per day, Tom will have $100 left when Jerry has spent all his money. If Tom spends $3 per day and Jerry spends $9 per day, Tom will have $220 left when Jerry has spent all his money. How much did Jerry have?
tia

[excelhub]

zanen:

excelhub:

[quote=\"zanen\"]someone help with me my hw pls Andy sold thrice as many $5 T-shirts as $10 T-shirts. He also sold twice as many $10 T-shirts as $20 T-shirts. He collected $160 more from selling $5 T-shirts than from selling $20 T-shirts.

every $15 (3* $5), he will have $10 (1*$10)

every $20 (2 * $10 ), he will sell $20 (1*$20).

hence,

every 1 set : 6 ($5), he will have 2 ($10) & 1 ($20).

total, $160/10, 16 sets.

thankyou you know this qns too? Tom and Jerry each has some money. If Tom spends $9 per day and Jerry spends $3 per day, Tom will have $100 left when Jerry has spent all his money. If Tom spends $3 per day and Jerry spends $9 per day, Tom will have $220 left when Jerry has spent all his money. How much did Jerry have?
tia [/quote]
we look at Jerry as he will definately have lesser money.

if he spent $3, he will have 3x days to spend.
if he spent $9, he will have x days to spend.

tom, will have $9 * 3x = $27x + $100.
tom, will have $3 * x = $3x + $220.

difference of 15x = $120.
x = 8.

[MathIzzzFun]

Ready2WORK:

tianzhu:

[quote=\"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:[/quote]for isosceles triangle, only 2 sides are of same length ie the base (in this case = y/4) is not of the same length of the other 2 sides.

cheers.

[MathIzzzFun]

Ready2WORK:

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.

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. [/quote]for this question, tianzhu interpretation is correct. If the \"mid-point thickness\" of the \"leaf\" is equal to half radius, the 3 outer circles will not be touching each other, using trigo/pythgoras theorem.

http://i47.tinypic.com/90t2cz.png\">

cheers.

[anneshirleygilbert]

tianzhu:

Essential:

Hi Tian Zhu thank you for your help for earlier question. One more question from Nanyang Prelim 2012. Q13. both shops. ABC and XYZ , offered a 15% discount for the same type of mattress. If Mr Muthu were to buy from shop XYZ ,he would have paid $38.25 less than the discounted price in shop ABC. a) What was the discounted price in the shop ABC ?

b) the original price of the mattress in Shop ABC was $1510. what was the minimum percentage discount it must offer so that the discounted price in shop ABC would be lower than the discounted price in Shop XYZ? Give your answer connect to the nearest percent.Thankyou in adv

Hi

15% ------- 38.25

100% ------- 255 (original price in XYZ)

For ABC ------ 255*100/85 ------- 300

a) Difference -------300 – 255 ------- 45

For (b)

Discounted price in ABC -------- 1510*0.85 ------ 1283.50

Discounted price in XYZ -------- 1283.50 – 38.25 ------- 1245.25

1510 – 1425.25 ------- 264.75

264.75/1510*100% ------- 18%

Best wishes

Hello Tianzhu,

I've not followed this thread for several days..... until now.

But, I have some trouble following your steps in this question. Can you help?