PSLE - New Format for Maths

[parentof3]

justsay:

My son told me the correct answer should be 74 not 71. Because after buying 71 curry puffs there is a balance of 240cents for another 3 curry puffs. Therefore answer should be 74.

The correct answer is 71. $2.40 left after 68 curry puffs. so 68 + 3 = 71.[/quote]

paisei.. my son remember wrongly. The answer is 71. Thanks

[meyya]

mathsparks:

haha I was wondering also. The only post that says Maths is easy..

my girl also told the maths is very difficult and time is not enough to do.

paper 1 can. paper 2 hard lah

[mathsparks]

meyya:

my girl also told the maths is very difficult and time is not enough to do.


paper 1 can. paper 2 hard lah

Tell her not to worry. Even perfect scorers can't finish, make mistakes. Plus it's a new syllabus and with moderation, the kids will do just fine.

[James Ang]

leungyc:

If the 3 lines are of the same length, then the angle of the intersecting chord cannot be 90 degree. you can do a mathematical proof that this angle will not be 90 degree, if the 3 lines of the triangle are of same length

The 3 lines are part of a circle or an arc. Therefore the 3 lines are equal radii of the circle and since the centre line is also the line of symmetry, it should be correct that the angle between the centre line and the chord is perpendicular to each other.

[kiasiparent]

Joy:

Hi


Can i check with you , is there any other information given besides the diagram?thanks

rgds

Secondary school method lol.

Angle at centre = 2 angle at circumference.

60 / 2 = 30 degrees

Opposite angle of cyclic quad
180 - 30 = 150 degrees.

[Bl8de]

Ultra KS:

http://www.postimage.org/image.php?v=TsqLCI9\">

">

May I know how did you derive ML = LK and AC?

[happypoppy]

Hi Bl8de,


It was given in the question that AD = AC = AB.

Since AC is perpendicular to BD, AC = KL (which in turn) = LM (as this is a square) = BD (question states that ML and BD are parallel).

Once it has been established that BD = AD = AB, triangle ADB is essentially an equilateral triangle. Therefore angle DAB = 60 degrees and angle DAC = 60 degrees / 2 = 30 degrees.

In view that triangle DAC is an isosceles triangle, angle b = 75 degrees and the required angle DCB = 75 degrees x 2 = 150 degrees.


NB: BTW, it was DH that solve the question for me. I was mulling over it for ages when he came over and solve it in 5 mins flat! I guess geometry is one of those questions that either you have the flair for it or you dont.

[turquoise]

Article about PSLE Math paper in Today newspaper:


http://www.channelnewsasia.com/stories/singaporelocalnews/view/1010464/1/.html

[Vanilla Cake]

pinky88:

mathsparks:

Speed Q is 11.06am

Raj's pay is $60 (It's part a which is $1170)
Curry puff and average height same.
Mathsparks' son.
Good luck for remaining subjects.

Anyone knows what's the qn on Raj's pay?

Hi pinky88,
Got the below information from this helpful http://www.blogger.com/profile/17918652673297709832.

Not in exact words
Raj's Qn
The total monthly salary for Raj and Devi was $ 4410. Raj earned $ 2070 more than Devi.
(a) What was Devi's monthly salary?
(b) If Raj worked 3 times as much as Devi, but Devi's pay for the same amount of work was $5 more than Raj's. what was Raj's pay?

Suggested solution
$(4410 - 2070) = $ 2340
$2340 / 2 = $ 1170
(a) Devi's monthly salary was $ 1170

$(4410 - 1170) = $ 3240 (Raj's monthly salary)
$ (3240/3) = $ 1080 (1 unit of Raj's salry)
$ (1170-1080) = $ 90 ( 1 unit difference between Devi's salary and Raj's salary)
$(90/5) = 18 ( Amount of work in a unit = 18 sets for Devi)
18 x 3 = 54 ( Amount of work in a unit = 54 sets for Raj )
$(3240/54)= $60
(b) Raj's pay was $ 60

Average height's Qn
The average height of a group of children was calculated as 139.4 cm. The height of 1 child was recorded wrongly as 129 cm. His correct height was 192 cm. The correct average height of the children should be 142.4 cm. How many children were there ?

Suggested solution
142.4 - 139.4 = 3
192 - 129 = 63
63 / 3 = 21
Number of children was 21

[pinky88]

Tks Vanilla cake for the qn & soln. u're really fantastic in Maths. Can solve all the prob. sums. The Uncle observer's blog was interesting. Tks again.