Tutor MathsGuru: Ask me for your burning Maths questions!

[Vanilla Cake]

beauty queen:

hello once again a 3 mark question,


This is from henry park 2010 prelim p2 question 10. (sorry dont have the image available)

The figure below is made up of three squares of sides 8 cm 12 cm and 20cm. Find the shaded area.

This one is not easy to explain without a diagram.OK, let me try.
Label the area as A for the dotted area at the top left corner (The one drawn dotted on top of square - 12x12)
Label Area B as the triangle with base as 12+20=32 cm and height as 12 cm.

Total (A+B+Shaded)=12x20+1/2x28x20=520 cm²
Area of A=8x12=96 cm²
Area of B =1/2x12x32=192 cm²
(520-96-192) cm² = 232 cm²

Area of shaded area = 232 cm²

Are you a P6 student? Due to my heavy homework load, I am not able to scan the diagram.Sorry.

PS: It's better that you scan your diagram as most of us do not have the Maths papers on hand.Uncle Tianzhu had provided the guidelines on how to post diagrams/pictures in KSP forum, pls read them.

[CJM]

Vanilla Cake:

CJM:

[quote=\"Dharma\"]
1u – 1p = 420 ------------- ( 1 )

Jug : 1p – 150
Kettle = 1u + 150

4p – 600 = 1u + 150
4p – 1u = 750 ------------ ( 2 )
( 1 ) + ( 2 )

3p = 1170
1p = 390
Amount of water in jug now = 1p – 150 = 390 – 150 = 240

Amount of water in jug now is 240 ml

Hi Dharma,

How to relate 1u & 1p ?
Need to draw model for this ?

Hi CJM,
Is this P4 Maths? While waiting for Uncle Dharma's reply, here's my suggested model solution for your review:

In the end
K: [][150][420][150]
J: [][150]

[150] must be in dotted form. I use red colour to represent it in dotted form.

4 times as much water in the kettle as the jug means 4 times of J=K.
4 units of J = 1 unit of K
4[]=[]+150+420+150
3[]=720
[]=240

1 unit of [] of J =240 ml ie Amount of water in the jug now = 240 ml

Hope this helps.
[/quote]Hi Vanilla cake,

Yes this is P4 question.

My boy drew the model same as what u hv drawn except that he did not define one of the unit in K as 150 instead he put the total of 3 units as 150 and 420 only :

K: [][150][420][ ]

3u : (420 + 150) /3

Can u pls advise why need to add another 150 to K ?

Thanks : )

[Vanilla Cake]

CJM:

Can u pls advise why need to add another 150 to K ?

Because the kettle received 150 ml of water from the jug.

[Hiroii-kun]

Dear gurus, please help with this qn.


There are 2 bags of stones labeled A & B. In bag A, there are 350 black stones and 500 white stones. In bag B, there are 400 black stones and 100 white stones. How many black and white stones should be transferred from bag B to bag A so that 50% of stones in bag A and 75% of stones in bag B are black?

[Vanilla Cake]

Hiroii-kun:

Dear gurus, please help with this qn.


There are 2 bags of stones labeled A & B. In bag A, there are 350 black stones and 500 white stones. In bag B, there are 400 black stones and 100 white stones. How many black and white stones should be transferred from bag B to bag A so that 50% of stones in bag A and 75% of stones in bag B are black?

This question is similar to RGPS 2009 P6 SA1 Paper 2 Q18 and pls refer to http://psle2010a.blogspot.com/2010/04/percentage-p6-2009-sa1-p2-rgs-q18_5512.html for reference while waiting for others to post their solutions.

Need to go to school now and sorry that I don't have time to post the solution for this question.The answer is 175 black and 25 white stones should be transferred from bag B to bag A so that 50% of stones in bag A and 75% of stones in bag B are black.

Hope that others like Uncle Dharma will help to check my answers and post the solution.

[Hifive]

Hi kancheongmum


Thanks for your solution.

Can you pls explain how do you work out the height of the shaded triangles?

Thanks!

[Hifive]

Hi everyone


Need help with this question
Source : ACS (Primary) SA2 2009 - P5

In the figure, a rectangular piece of paper is folded at two of its corner X and Z as shown. Find angle XYZ.

http://postimage.org/image/35kpmw8xw/

Thanks in advance.

[Vanilla Cake]

Hifive:

Hi kancheongmum


Thanks for your solution.

Can you pls explain how do you work out the height of the shaded triangles?

Thanks!

Hi Hifive,

While waiting for kancheongmum's reply, pls see whether my explanation helps or not?

(a) Look at the bases of the 2 triangles that are 2m, the total height of them is 24m
(b) Look at the bases of the 2 triangles that are 6m, the total height of them is 12m
(c) Calculate total area of the 2 triangles with bases as 2m-> Total area =1/2x2x24=24m²
(d) Calculate total area of the 2 triangles with bases as 6m-> Total area =1/2x6x12=36m²
(e) Add (24+36)m²= 60m² which is the total shaded area
(f) 2 marks is in your bag.

VC's mum

[Hifive]

Hi VC’s mum


yes, yes, your explanation helps! Thank you so much!

[Vanilla Cake]

Hifive:

Hi everyone


Need help with this question
Source : ACS (Primary) SA2 2009 - P5

In the figure, a rectangular piece of paper is folded at two of its corner X and Z as shown. Find angle XYZ.

http://postimage.org/image/35kpmw8xw/

Thanks in advance.

Hi Hifive,

This question is not easy to explain as DD2 add dotted lines and labeled the angles in the original diagram. As both my daughters are in school, I am not able to scan DD2's solution.

Here's DD2's solution:

(180⁰-60⁰)÷2=60⁰
180⁰-90⁰-60⁰=30⁰
Angle XYZ=180⁰-30⁰-30⁰-20⁰-20⁰ = 80⁰

Pls wait for others to post their solutions as it's not easy to understand without adding dotted lines and labeling the angles in the original diagram.
BTW, Observer had posted his http://psle2010a.blogspot.com/2010/09/angles-p5-2009-sa2-acs-p2-q11.html for your question in his blog.Check it up.

VC's mum