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[Vanilla Cake]

Maths Monster:

Vanilla Cake:

[quote=\"firebird\"]from Paper 2 CHIJ St Nicholas Girl's School Preliminary Exam 2009:

Question 9,
I apologise for not inserting the diagram, which I am unable to.
The figure below is not drawn to scale. PQRS is a square and CBRD is a rectangle. BRE is a straight line. Given that angle DRF = 136 degree and angle SHD = 129 degree. Find the ratio of angle HRD to angle ERF.

Hi firebird,
There is a typo error in your question (see highlighted in red colour). The original question asked for the ratio of angle HRB to angle ERF and not angle HRD to angle ERF.

Angle DHR=180⁰-129⁰ =51⁰
Angle HRB=Angle DHR=51⁰ (alternate angles)

Angle DRB=Angle DRE=90⁰ (BRE is a straight line)
Angle ERF=136⁰-90⁰ = 46⁰

Ratio of angle HRB to angle ERF = 51:46

firebird:

Question 17
At carpark P, the number of lorries to that of vans was in the ratio 3:7.
At carpark Q, the number of lorries to that of vans was in the ratio 8:9.
When 40% more lorries from an industrial estate entered carpark P and 20% of the vans at Q moved to carpark P, there were 76 fewer lorries at carpark P than Carpark Q. How many vehicles were there althogether at the two carparks finally?

Before
Carpark P
L : V
3 : 7

Carpark Q
L : V
8 : 9

1.4x3u=4.2u (40% more lorries from an industrial estate entered carpark P)
0.2x9u=1.8u (20% of the vans at Q moved to carpark P)

After
Carpark P
L : V
4.2 : 8.8

Carpark Q
L : V
8 : 7.2

(8-4.2)u = 3.8u
3.8u = 76
u = 20
(4.2+8.8+8+7.2)u = 28.2u
28.2u = 28.2x20=564

Finally, there were 564 vehicles at the two carparks.

Hi Vanilla,

A question on the \"Lorry and Van\" problem. In your working, it seems that the ratio given in the two car parks are \"linked\", however it is not given in the question that the ratio in the lorry and van in car park A & B is 3 : 7 : 8 : 9 initially. Not sure how do you derive this from the question? Can you explain? TIA

Thanks,
MM[/quote]Hi MM,
Sorry if my workings were misleading.This \"Lorry and Van\" problem was discussed over http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&postdays=0&postorder=asc&start=880 and by http://prischoolmaths.blogspot.com/2009/10/ratio_06.html who stated it as an unfair question. Hopefully, you may wish to add your comments for this \"unfair\" question so that we can learn more on how to solve this question.
Thanks.

[Maths Monster]

delete

[ttyh]

I’m sorry to post this but I’ve absolutely no clue on this P2 Math question.

It is a picture showing a mother cat watching 2 kitten playing a ball of wool.
Question : Write a multiplication story for this picture…

Pls help me!!!

[firebird]

Dear Vanilla cake


Good morning.

Very sorry for the incomplete question. Thank you detailed working.

With best regards
firebird

[Chrislee]

Good morning, please help me with the following sum.


I have 2 pairs of hamsters. Each pair with give birth to 2 pairs of hamsters in every 1 day. How many hamsters will there be 4 days later?
Answer: 324

Thanks a lot!

[CoffeeCat]

Chrislee:

Good morning, please help me with the following sum.


I have 2 pairs of hamsters. Each pair with give birth to 2 pairs of hamsters in every 1 day. How many hamsters will there be 4 days later?
Answer: 324

Thanks a lot!

Before Day 1: 2
After Day 1 : 4 (new born) + 2 = 6
After Day 2 : 12 (new born) + 6 = 18
After Day 3 : 36 (new born) + 18 = 54
After Day 4 : 108 (new born) + 54 = 162 pairs

162 pairs = 324 hamsters.
If you look at the pattern, 2*3 = 6, 6*3 = 18, 18*3= 54, 54*3=162

[Herbie]

I have one qn.

Kent had a collection of 160 toys. 11/20 of them were soft toys.
After he gave away some of the soft toys away, the no. of soft toys left made up of 2/5 of the remaining collection. How many soft toys did he give away?

Can help to provide the solution?
Tx

[CoffeeCat]

Herbie:

I have one qn.

Kent had a collection of 160 toys. 11/20 of them were soft toys.
After he gave away some of the soft toys away, the no. of soft toys left made up of 2/5 of the remaining collection. How many soft toys did he give away?

Can help to provide the solution?
Tx

At first, 88 soft toys, 72 non soft toys.
After giving some away, the 72 non soft toys make up 3/5 of remaining.
Therefore number of soft toys left is 48.
Number of soft toys given away = 40

[Sun_2010]

Hi,


DD is struck at this question . I tried it too- cant get it.
Can some one help?
Question 6 of the sample paper for APMOS
http://www.hci.sg/aphelion/apmops/sample_questions/Invitation%20Round%20Sample%20Questions.pdf

Thanks

[CoffeeCat]

Sun_2010:

Hi,


DD is struck at this question . I tried it too- cant get it.
Can some one help?
Question 6 of the sample paper for APMOS
http://www.hci.sg/aphelion/apmops/sample_questions/Invitation%20Round%20Sample%20Questions.pdf

Thanks

What a coincidence, I was explaining that question to a student at the time when you post this.
This happens to belongs to a class of geometry questions which solutions requires the construction of an equilateral triangle.
At first glance, the clue AB=DC look useless because the 2 lines are far away and usually we think of isoceles triangle when we heard of 2 equal lines in angles.
Imagine that there is a perpendicular line passing through the midpoint of BC, then reflect the triangle BDC about that line, so that there is now a new point D' in the interior of the triangle such that angle BD'C = angle CDB, and angle D'BC = angle DCB = 20 deg.
Notice CD = BD' = AB ( ABD' is isoceles) and since angle ABC=80 deg, angle ABD' = 80-20=60 deg, thus ABD' is an equilateral triangle.
We want to find angle BDC, which is equivalent to finding angle CD'B.
The next step will be hard to see if your equilateral triangle is not drawn properly, because the point D' is actually directly midway between A and B. angle BD'C = angle AD'C = (360-60)/2 = 150deg.