Q&A - PSLE Math

[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

[Dharma]

tianzhu:

Other than Guess and Check, what are the other alternatives to solve this problem?


Annie wrote her mother's age followed by her own age to form a 4-digit number.She used the difference between their ages to subtract from the 4-digit number. Then Annie obtained the number 4489.What was Annie's age ? (RGPS P6 Prelim 2008 Q47)

The 4 digit number is ABCD ... AB is mother's age while CD is Annie's age.

ABCD - (AB - CD) = 4489

ABCD = (AB00 + CD) -( AB - CD) = 4489

AB - CD > 10 .... AB = 45

4500 - CD - 45 + CD = 4489
2CD = 34
CD = 17

Annie's age = 17

[Tang]

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)

15 cats 15 rats 15 min
1 cat 1 rat also 15 min
Hence 60 cats 60 rats also 15 min