Q&A - PSLE Math

[tianzhu]

ozora:

3.I have some almond n butter cookies. If she packs 1 almond n 1 butter cookie, there will be 60 butter cookies left. If she packs2 almond with 3 butter, there will be 50almond cookies left. How many cookies r there in all?

Hi

You may use MD to solve it. I’ll give you some pointers.

Draw 2 big boxes. Add 60 butter cookies. For illustration purposes here, let’s call 1 box “1 part”

Draw two smaller boxes to show almond cookies. Add 50 to them. Next add 3 identical boxes to show butter cookies. Let’s name each small box “1 unit”

The number of cookies in both scenarios is the same.

1 part ----- 2 units + 50

Compare butter cookies
2 units + 50 + 60 ------ 3 units
1 unit ----- 110

Number of cookies ------ 5 units + 50 ------ 600

Best wishes

[Daddy]

Hi,

Need help.

1. Gina spent $270 on a CD player and 2/9 of the remainder of her money on a handbag. Then, she bought blouse for $60. If she had 1/9 of her money left, how much did she have at first?

2. Raphael had $40 less than Sam. When he spent 1/8 of his money and Sam spent 3/4 of his money, Raphael had $80 more than Sam. How much money did Sam have left.


Thanks

[MathIzzzFun]

Daddy:

Hi,

Need help.

1. Gina spent $270 on a CD player and 2/9 of the remainder of her money on a handbag. Then, she bought blouse for $60. If she had 1/9 of her money left, how much did she have at first?

2. Raphael had $40 less than Sam. When he spent 1/8 of his money and Sam spent 3/4 of his money, Raphael had $80 more than Sam. How much money did Sam have left.


Thanks

Hi

http://i52.tinypic.com/2i11tgy.jpg\">


http://i51.tinypic.com/23mx1f5.jpg\">

cheers.

[tianzhu]

Hi


CHS SA2 Q18 2010
\t
This question touches on two concepts

(a) ------ Constant Difference or Unchanged Difference
(b) ------ Changed Quantities

I don’t have time to prepare slides. Please try to consolidate the solutions in tabulated form as it’ll be neater.

Speakers
Male ------ 8
Female ------ 5
Difference -------3

Participants
Male ------ 1 ------ 10
Female ------1 ------ 10

Total number
Male ------- 6 --------18
Female ------ 5 -------15
Difference -------1 ------ 3

For part (a)

Students should note that this is a ratio question involving “Constant Difference” or “Unchanged Difference”.

The difference between the male and female speakers and the difference between men and women (speakers + participants) in the conference are the same.

Total number ------ 33 units
33- 13 ------ 20

20 units are to be divided equally between male and female participants.

Ratio of male speakers to male participants -------8:10 ------4:5

For part (b), the question involves “Changed Quantities concept”. Here, the quantities at the beginning and the end are different.

At first

Participants
Male ------ 10 units - 40
Female -----10 units + 60

In the end
Male ------ 3 parts
Female -----4 parts

Equalise the parts or cross multiply.

40 units -160 ------30 units +180
10 units ------ 340
1 unit ------34

Number of speakers ------13*34 ------ 442

Best wishes

[tianzhu]

Hi


CHS SA2 Q17 2010

I prefer to change percentages into units first before proceeding further with the solution.

Daniel ------140% ------- 7 ------ 35
Brandon ------ 100% ------ 5 ------ 25

Daniel and Brandon each give 20% of their share to Calvin
Daniel ------ 7
Brandon ------ 5

Calvin receives 12units from Daniel and Brandon
12 units ------ 80%
15 units ------ 100%

In the end, Calvin had 27 units and Daniel had 28 units.

28-27 ------1
1 unit ------20

At first, Brandon had (25*2) or 500 stickers.

Best wishes

[tianzhu]

ozora:

Thanks tianzhu.

Hi

Good Morning.

You're welcome.

Best wishes

[tianzhu]

PiggyLalala:

Just want to say A BIG THANK YOU to you. :thankyou:

Hi

Good Morning.

You're welcome.

Best wishes

[htn]

P5G:

htn:

Hi Vanilla Cake


Can u teach me how to solve nan hua prelim paper 2 Q16 b?
TIA

Hi Uncle/Auntie htn,

For (16b), you just need to add the two areas together then use the volume
of water divide by the total area as follows:

500 + 300 = 800 cm2

6000/800 = 7.5 cm

P5G

Thanks

Auntie htn

[bluesky63]

small:

Hi fxchow,


HTH but I am not so sure on my answer for part (b).

a)
Given that 30% of the pupils in Sch A is 45 more than 40% of the pupils in Sch B.
0.3A - 45 = 0.4B --> x10

3A = 4B + 450 ----- equation (1)


If 10% of the pupils in Sch A leaves to join Sch B, there will be 200 more pupils in Sch A than Sch B
0.9A – 200 = 0.1A + 1B
0.8A = 1B + 200 --> x10

8A = 10B + 2000 ----- equation (2)


We will need to eliminate A to get B;

equation (1) x 8:
24A = 32B + 3600

equation (2) x 3:
24A = 30B + 6000

32B + 3600 = 30B + 6000
2B – 6000 – 3600
2B = 2400
1B = 1200

There are 1200 pupils in Sch B


b)
from equation (1) :

3A = 4 X 1200 + 450
3A = 4800 + 450
3A = 5250
1A = 1750 (100%)

The different between School A and School B is:
1750 – 1200 = 550

1750 = 100%
550 = 550/1750 x 100%
= 1100 / 35 %
= 31 3/7%


There are 31 3/7% percent less pupils in Sch B than Sch A

Hi, can anybody show us the working using modelling (blocks) Thanks !

[P5G]

htn:

P5G:

[quote=\"htn\"]Hi Vanilla Cake


Can u teach me how to solve nan hua prelim paper 2 Q16 b?
TIA

Hi Uncle/Auntie htn,

For (16b), you just need to add the two areas together then use the volume
of water divide by the total area as follows:

500 + 300 = 800 cm2

6000/800 = 7.5 cm

P5G

Thanks

Auntie htn[/quote]
Hi htn,

I am sorry that P5G has given you the wrong volume. She should not have used 6000 cm3 that she worked out in part (a). The volume should be the amount flowed out from Tap B only and not the net volume from the tank.

The volume should be 800 x 20 = 16 000 cm3.

Combined area = 300 + 500 = 800 cm2

Height of water in 2 containers = 16 000 / 800 = 20 cm


P5G mum.