Q&A - PSLE Math

[lizawa]

hypergatak:

hi


Appreciate your input to the following question:-
1/1x2 + 1/2x3 +1/3x4 +...........................................1/2009x2010 +1/2010x2011.

You need to see the pattern that
1/1x2 = 1/1 - 1/2
1/2x3 = 1/2 - 1/3
1/3x4 = 1/3 - 1/4 etc

So expand the question, you get
1/1 - 1/2 + 1/2 -1/3+1/3 -1/4.......+ 1/2010 - 1/2011
All terms in the centre are eliminated except first and last
= 1/1 - 1/2011 = 2010/2011

[hypergatak]

Thanks for your help.

[speedmaths.012624com]

hypergatak:

hi


Appreciate your input to the following question:-
1/1x2 + 1/2x3 +1/3x4 +...........................................1/2009x2010 +1/2010x2011.

P6 pupils (2012) can learn to answer such questions in our PSLE Maths camps.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=43&t=25433


Speedmaths.com

[Chan09]

Some help on this:

Mr Tan saves 15% of his salary. His savings increased by $18 when his salary increases by 5%. what is his salary before the increase?
Ans:$2400

[lizawa]

Chan09:

Some help on this:

Mr Tan saves 15% of his salary. His savings increased by $18 when his salary increases by 5%. what is his salary before the increase?
Ans:$2400

Before :
Savings : 15%; salary : 100%
After :
Salary : 105%
savings -> 15% x 105 = 15.75%
0.75% -> 18
(salary before increase) 100% -> 18/0.75 x 100 = 2400

[JadeDry]

Hello,


I would appreciate input on this question:

Simplify:

((3 X squared-Y cubed) / (8 Z-squared)) / ((9 Y-squared)/10Z)) x ((6 Y-squared- Z cubed) / 5X))

My answer is ((X-Y cubed- Z squared) /2 ) Is this correct?

Thanks in advance for your assistance.

[sleepyqueen]

JadeDry:

Hello,


I would appreciate input on this question:

Simplify:

((3 X squared-Y cubed) / (8 Z-squared)) / ((9 Y-squared)/10Z)) x ((6 Y-squared- Z cubed) / 5X))

My answer is ((X-Y cubed- Z squared) /2 ) Is this correct?

Thanks in advance for your assistance.

Yes this is what I get also, hope we are right.
answer: (xy3z2)/2

[linden2000]

Hi. For the Nanyang Pri School’s P6 CA1 paper 2 question 18 (last question of paper 2), does anyone have any idea what is the missing number in the following sentence?


"The total area of Triangle A and Triangle B is _______of the area of Triangle C."

Other than algebra, how would we solve this question?

Many thanks.

[whitety]

Hi, I need help to solve 2010 Rosyth CA1 Paper 2 qn 5.


Mrs Tan takes 15 mins to paint a wall and Mr Tan takes 10mins to paint the same wall. If both of them paint the wall together, how long will they take to paint the wall?

Many Thanks!

[speedmaths.012624com]

whitety:

Hi, I need help to solve 2010 Rosyth CA1 Paper 2 qn 5.


Mrs Tan takes 15 mins to paint a wall and Mr Tan takes 10mins to paint the same wall. If both of them paint the wall together, how long will they take to paint the wall?

Many Thanks!

You can solve this without using fractions in the working.

Use a common multiple of 15 and 10, say 30.

Mrs Tan takes 15 mins to paint a wall.
In 30 mins, Mrs Tan can paint 2 walls.
Mr Tan takes 10mins to paint the same wall.
In 30 mins, Mr Tan can paint 3 walls.

In 30 mins, Mrs Tan and Mr Tan can paint 2 + 3 = 5 walls.
Paint 5 walls in 30 mins
Paint 1 wall in 30/5 = 6 mins.

Pupils can learn to solve such problems in our Maths camps on 10 Dec and 17 Dec.
Please see:
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=43&t=25433

Pupils can also learn to solve similar problems from this book \"Go For A-* Volume 2\", which is available from any Popular Book stores.