Q&A - PSLE Math

[small]

thanks for your time


If Kenny gives 18 marbles to Andrew, he will have thrice as many marbles as Andrew. If Andrew gives 12 marbles to kenny, he will have 1/9 of the number of marbles that kenny has. How many marbles does Kenny have at first?

My working as below but I have no idea how to expalin this to my DD. :stupid:

http://img35.imageshack.us/img35/4531/phpc8s7wm.png\">

[atutor2001]

ChiefKiasu:

More headache for us parents? Heheh. It's good that we see these questions for ourselves... that way we respect our children even more if they managed to get the questions right.


Quick question: Which Primary level are these questions for?

Hate to sound boastful. But these are \"standard\" questions that all P6 must know in order to pass comfortably.

That is the sad state of our system.

The interesting thing is that most students struggled through in P5 but becomes quite confortable by P6.

[tianzhu]

Hi, small


Please read your PM.

Best wishes

[Tang]

small:

thanks for your time


If Kenny gives 18 marbles to Andrew, he will have thrice as many marbles as Andrew. If Andrew gives 12 marbles to kenny, he will have 1/9 of the number of marbles that kenny has. How many marbles does Kenny have at first?

My working as below but I have no idea how to expalin this to my DD. :stupid:

http://img35.imageshack.us/img35/4531/phpc8s7wm.png\">

K [_1u_][_________________8u______________________]
K [_1u_][12][_18][_1u_][12][_18][_1u_][12][_18][_18][12]
A [_1u_][12][_18]

6u -> 4 x (12+18 ) = 120 (compare K)
1u -> 120 / 6 = 20

9u -> 9 x 20 = 180

180 - 12 = 168

Kenny has 168 marbles at first.

[small]

Thnaks TianZHu and Tang. :celebrate:

[tianzhu]

Thank you for your help.


Q45 RGPS SA2 2007 ----- I am referring to the first solution. How to prove that (72+84) equals to half the area of the rectangle?

http://www.wendykoh.com/07/primary6-rgs1-maths.pdf

[atutor2001]

tianzhu:

Thank you for your help.


Q45 RGPS SA2 2007 ----- I am referring to the first solution. How to prove that (72+84) equals to half the area of the rectangle?

http://www.wendykoh.com/07/primary6-rgs1-maths.pdf

The base of both triangles are equal and is equal to the breadth of the rectangle. The sum of the heights of both triangles is equal to the length of the rectangles.

Therefore, their combined areas is equal to half the area of the rectangle.

[faith2u]

Meimei would be given 20cent for each greeting card she sold. In addition, she would get $4 for every 10 greeting cards sold… How many cards did she sell if she earned $80?

[James Ang]

faith2u:

Meimei would be given 20cent for each greeting card she sold. In addition, she would get $4 for every 10 greeting cards sold.. How many cards did she sell if she earned $80?

if she sells 140 cards, she earns (140/10)x6 = 84
if she sells 139 cards, she earns (130/10)x6 +9x20c = 78+1.8 = $79.80

so she could not have earned $80, she is owed $4.

by the way, people smart about maths should also use maths intelligently to make decision. Assuming in above case, if she earns $79.80 selling 139 cards, she should be intelligent enough to know that by selling one more card she earns $4.20 and not $0.20, so logically she should buy that one card herself!

[janice099]

Hello there, this is my first reply. Thanks for helping


John can walk to school in 40 minutes while his brother, Jack, takes 20 minutes. If they both start walking to school at the same time, how long will it take for John to be 2/5 as far as Jack.