Q&A - PSLE Math

[Vanilla Cake]

leesf:

http://postimage.org/image/j1m6ikhw/

Area of square : Area of rectangle
1 : 3
5 : 15

Area of unshaded square : Area of unshaded rectangle
2 : 7
4 : 14

Shaded area -> (5-4)u= u or (15-14)u = u
u=20 cm²
Area of square = 5u = 5x20cm² = 100 cm²
10 cm x 10 cm = 100 cm²
Length of the square = 10 cm

[kancheongmum]

Vanilla Cake:

firebird:

4) The Quesion 15 Paper 2 has a diagram. Need to find the shaded figure. Very sorry, I do not have the scanner to upload the question. Please help if you can.

Dear firebird,
Pls refer to solution by http://psle2010a.blogspot.com/2010/09/area-p6-2010-sa2-rosyth-p2-q15.html and pls refer to http://1.bp.blogspot.com/_EG8oMs7TIYA/TIrJ3Pk8mkI/AAAAAAAAASM/eLmp3ZHjcek/s1600/MathsP610AreaRosythA15.jpg for bigger view.

OR

Solution by http://4.bp.blogspot.com/_hEGsaDYqgAQ/TIuqCEjKWlI/AAAAAAAABY0/qIYx5Bn65ns/s1600/qn.jpg:

Let AG be x cm.
Then GB = 12-x
Triangle AGF is similar to Triangle ABC, hence AG = GF = x
Tiangle BGF is similar to Triangle BAE, hence
BG/GF = BA/AE
=> (12-x)/x = 12/6 (since AB = 12, AE = 6)
=> 12-x = 2x
=> x=4
Area of Triangle DEF = 1/2 x ED x AG = 1/2 x 6 x 4 = 12
Area of Triangle DFC = 1/2 x DC x (BC - GF) = 1/2 x 12 x (12-4) = 48
Hence, Area of shaded region = 12 + 48 = 60 cm2.

Hi Vanilla Cake

I hope you don't mind about my comments. The solution you posted is too complicated and I think similar triangle is not in the syllabus. Your method is more for secondary level. I am looking at the question because DS cannot solve. Using Observer's solution to explain to him, he still cannot understand. Finally after looking at the diagram for sometime I used line of symmetry AC (diagonal of the square) and the rest of the solution fall into place.

[tianzhu]

kancheongmum:

Finally after looking at the diagram for sometime I used line of symmetry AC (diagonal of the square) and the rest of the solution fall into place.

Hi kancheongmum

Good Morning

I can’t resist logging in just to say Thank you for a brilliant solution.

You've given us a key to unlock this question.A simple move equivalent to a well measured pass floated by a top footballer in a soccer match.

Best wishes

[tianzhu]

firebird:

Dear Tianzhu sir


Thank you very much for your answer.

With best regards
Firebird

Hi firebird

Good Morning.

You're welcome.

Best wishes

[Dharma]

http://postimage.org/image/2iacuden8/

[Vanilla Cake]

firebird:

4) The Quesion 15 Paper 2 has a diagram. Need to find the shaded figure. Very sorry, I do not have the scanner to upload the question. Please help if you can.

Hi firebird,

http://www.onsponge.com/forum/35-thinkingmathonsponge/5406-rosyth-school-2010-p6-prelim-paper-2-q15-4-marks.html.

VC's mum

[cycjca]

tianzhu:

cycjca:

1) Mrs Chua has just enough money to buy 4 kg of crabs & 3 kg of prawns. However she bought 2 kg of crabs & 4 kg of prawns & had $4.50 left. If she exchanged the 3 kg of crabs with 3 kg of prawns, how much money would she have left?

If 2kg of crabs is changed to 3kg of crabs, here's the solution.

Hope this helps.

Best wishes

http://farm5.static.flickr.com/4133/5019157330_02c85ba4c0_b.jpg\">

Hi Tianzhu

sorry my tardy response. It should be 3 kg. Thanks for you help. Really appreciate it.

[tianzhu]

cycjca:

Thanks for you help. Really appreciate it.

Hi

You're welcome.

Best wishes

[leesf]

Thanks to atutor2001 and teachingmum for your solutions.

[tianzhu]

Hi


Three interesting Speed questions.

Best wishes

Q1
Last Monday, Danny walked from home to market. For the first 5 minutes, he was walking at an average speed of 35m/min. When he realized that he was going` to be late by 4 minutes, he quickly increased his speed by 10m/min. As a result, he was early by 2 minutes. Find the distance between market and home.

Q2
Jacki’s mum leaves home at 12.35pm every day and arrives 25 minutes later at his school to pick him up. She always cycles at the same speed along the same route. One day Jacki was dismissed early at 12.30pm, so he started walking home at 6km/h, hoping to meet her along the way. He met her at x and got onto her bicycle. They reached home 15 minutes earlier than before. How far did Jacki walked before his mum picked him up?

Q3
Tony and Charles took part in a car race. Tony drove at a speed of 90km/h. Both of them did not change their speed throughout the race. When Charles had covered 1/3 the distance, Tony was 15km in front of him. Tony reached the finishing line at 9.35 a.m. At what time did Charles reach the finishing line?