Q&A - PSLE Math

[P5G]

Vanilla Cake:

Hi all,


Answer given by vlim is option (2) but I think that it should be option (3). Pls look into this question and advise the correct answer.Thks for your time and effort.
http://i53.tinypic.com/2yzdh4x.png\">
Option (1) - 1/6
Option (2) - 1/3
Option (3) - 2/5
Option (4) - 1/2

Hi Vanilla Cake,

Option (2) is correct.


This is how my mum worked out the answer.

Join opposite edges to get 6 equilateral triangles.

The area of the shaded triangle is equal to 2 equilateral triangle as its height is twice an equilateral triangle and their bases are the same.

So answer is 2/6 = 1/3, which is option (2).


By the way, do you know the answers to Chong Fu 2011 CA2 Science.

Should the answer for 39 be
a). A and D instead of A and F.
c). Kinetic energy --> Kinetic energy + ??? (No idea) instead of Kinetic energy --> Heat energy + Sound energy.


Please help. TIA.

[Vanilla Cake]

Hi Publica,


:imsorry: for the late reply as I was working on the Rosyth 2011 P6 Prelim Maths paper earlier on.

OK and will skip part (a) since you have no problem.
For part (b):
Given that angle BAD is a right angle ie 90 degree and AC=AD.
and angle CAB = 40 degree.
So angle CAD = 90 degree - 40 degree = 50 degree
Angle ACD = Angle ADC = (180-50)÷2 = 65 degree
But you know that angle ACB = 70 degree (given) and so you can find angle ABC = (180-40-70) = 70 degree which is the same as angle ACB.
This means that AB = AC = AD as this is the breaking point!
So, Angle ABD = Angle ADB = (180-90)÷2 = 45 degree.
Lastly, Angle BDC = (65-45) degree = 20 degree

Hope this helps and thks.

PS: Thks to P5G for the correction.

[Publica]

Vanilla Cake:

Hi Publica,


:imsorry: for the late reply as I was working on the Rosyth 2011 P6 Prelim Maths paper earlier on.

OK and will skip part (a) since you have no problem.
For part (b):

Given that angle BAD is a right angle ie 90 degree and AC=AD.
and angle CAB = 40 degree.
So angle CAD = 90 degree - 40 degree = 50 degree
Angle ACD = Angle ADC = (180-50)÷2 = 65 degree
But you know that angle ACB = 70 degree (given) and so you can find angle ABC = (180-40-70) = 70 degree which is the same as angle ACB.
This means that AB = AD as this is the breaking point!
So, Angle ABC = Angle ADB = (180-90)÷2 = 45 degree.
Lastly, Angle BDC = (65-45) degree = 20 degree

Hope this helps and thks.

Hi Vanilla Cake,

Many thanks for you to provide the solution. We understand now.

[P5G]

Vanilla Cake:

Hi Publica,


:imsorry: for the late reply as I was working on the Rosyth 2011 P6 Prelim Maths paper earlier on.

OK and will skip part (a) since you have no problem.
For part (b):

Given that angle BAD is a right angle ie 90 degree and AC=AD.
and angle CAB = 40 degree.
So angle CAD = 90 degree - 40 degree = 50 degree
Angle ACD = Angle ADC = (180-50)÷2 = 65 degree
But you know that angle ACB = 70 degree (given) and so you can find angle ABC = (180-40-70) = 70 degree which is the same as angle ACB.
This means that AB = AD as this is the breaking point!
So, Angle ABC = Angle ADB = (180-90)÷2 = 45 degree.
Lastly, Angle BDC = (65-45) degree = 20 degree

Hope this helps and thks.

Hi,

There is a slight typo-error.

So, Angle ABC = Angle ADB = (180-90)÷2 = 45 degree.

Correction: Angle ABC should be Angle ABD.

[Vanilla Cake]

P5G:

Hi Vanilla Cake,

Option (2) is correct.
This is how my mum worked out the answer.
Join opposite edges to get 6 equilateral triangles.
The area of the shaded triangle is equal to 2 equilateral triangle as its height is twice an equilateral triangle and their bases are the same.
So answer is 2/6 = 1/3, which is option (2).

Hi P5G,
Your mum is correct and option (2) is the correct answer. So, 2 precious marks gone and my younger sister got 98/100 for this Rosyth 2011 P6 Prelim Maths paper. :stupid:
Thks for the tips from your mum.

[raghupavithra]

The average height of 2 girls is 1.50m. The difference in their height is 0.4m. What is the height of the taller girl?


1.10
1.30
1.54
1.70
pls help

[tianzhu]

raghupavithra:

The average height of 2 girls is 1.50m. The difference in their height is 0.4m. What is the height of the taller girl?


1.10
1.30
1.54
1.70
pls help

Hi

2*1.5 -----3

3-0.4 ----- 2.6

2.6/2 ------ 1.3

1.3 + 0.4 ------ 1.7 (ans)

Best wishes

[tianzhu]

Hi


Hope this helps.

Best wishes.

http://farm7.static.flickr.com/6177/6160679750_ff917d0516_z.jpg\">

[zsqchx]

Please help me to solve Q 16 of Henry park 2011


Mr Lee took 7 hours to tavel from town A to Town B while Mr Wong took 8 hours to travel from Town B to Town A. Both of them did not change their speed throughout the journey. Both of them started off at the same time and moved towards each other. 3 hours later, they were 110 km apart. what was the speed Mr Lee was driving?

Thanks

[tianzhu]

zsqchx:

Please help me to solve Q 16 of Henry park 2011


Mr Lee took 7 hours to tavel from town A to Town B while Mr Wong took 8 hours to travel from Town B to Town A. Both of them did not change their speed throughout the journey. Both of them started off at the same time and moved towards each other. 3 hours later, they were 110 km apart. what was the speed Mr Lee was driving?

Thanks

Hi

Good Morning.

As in any question on “Speed”, it’s helpful to draw a simple diagram showing the relationships between two motorists.

Use a common multiple of 56 (7 and

Mr Lee
1h ------ 8 units

Mr Wong
1h ------7 units

In 1h they travelled 15 units
In 3h, they travelled 45 units.

56 – 45 ------11
11units ------ 110

1 unit ------ 10
8 units ------80

Mr Lee ------- 80km/h

Best wishes