Q&A - PSLE Math

[tianzhu]

Hi Drdj


You don't have to click on quote each time you want to post new questions.Use it when you want to refer to it.

For new post without referencing, just click on post reply.

[Dharma]

Drdj:

Hi there,


Please help me with the following :

NanHua Prelim 2008

Qn 24
15 cats can catch 15 rats in 15 minutes. How long does it take 60 cats to cath 60 rats? [Ans = 15 mins - how do you know which qty to stay constant/change]

Thanks in advance

15 cats - 15 rats - 15 mins
1 cat - 15 rats - 225 mins
1 cat - 60 rats - 900 mins
60 cats - 60 rats - 900/60 = 15 mins
(Only change 1 independent variable at a time)

[Dharma]

Hi Drdj,


If Amy gives $3.50 to Beth

At last
Amy : 1 unit
Beth : 1 unit
Carrie : 1 part

At first
Amy : 1 unit +$3.50
Beth : 1 unit - $3.50
Carrie : 1 part

If Beth gives $3.50 to Amy

At last[/u]
Amy : 1 unit +$7
Beth : 1 unit - $7
Carrie : 1 part

1 unit + $7 = 3 units - $21
2 units = $28
1 unit = $14

1 part = 2 units = $28

Amt of money 3 of them have = 2 units + 1 part = $28 x 2 = $56

[tianzhu]

Thank you for your help.


RGPS SA2 2008 Q43.


http://www.postimage.org/

[joyceling]

tianzhu:

Thank you for your help.


RGPS SA2 2008 Q43.


http://www.postimage.org/

the answer is 2cm.

[Happygolucky]

HI Tianzhu,


If I’m not wrong , one of the cubes at the uppermost layer was not in the question.

Is the answer 2 cm?

[joyceling]

cubes for each level is (top to bottom ) 1,3,6

water difference between top 2 levels and bottom level is the cubes difference: 8 cubes=1120-352x3=64, so each cube is 8 cm3
so the height is 2cm

[tianzhu]

Happygolucky:

HI Tianzhu,


If I'm not wrong , one of the cubes at the uppermost layer was not in the question.

Is the answer 2 cm?

Hi

This question is from http://www.misskoh.com
Join the free membership to view the question from RGPS.
I guess one of the cube is not in the question as it looks different from the others.

[tianzhu]

Perhaps girls of 2008/9 RGPS would like to comment on the extra cube shown in the picture.


My gut feeling is it’s not there.

[Dharma]

tianzhu:

Perhaps girls of 2008/9 RGPS would like to comment on the extra cube shown in the picture.


My gut feeling is it's not there.

You're right. It was hand-drawn (its the one at the top row - on the righthand side)

Cube size - 2cm x 2cm x 2cm
Height of container = 6cm