Q&A - PSLE Math

[tianzhu]

Hi


NY SA2 Q16 2010

Each boy ate 2/9 of a pizza and each girl ate 1/6 of a pizza
Use a common multiple of 18

Boys ----- 4 units
Girls ----- 3 units

The girls received thrice as many pizzas as the boys.

Boys ----- 4 units
Girls ----- 12 units

12 – 3 ----- 9

9 units -----4.5 pizzas

16 units ----- 8 pizzas

Best wishes

[ozora]

Need help:1. Don walked from home to school. He was walking at an ave speed of 35m/min for the 1st 5min. He increased his speed by 10m/min when he realized he was going to be late for 4 mins. As a result, he was early by 2 mins. What is the distance bet the school n home?

2.when mrs Toh was 40 years old, her son was twice her daughter’s age. Mrs Toh would be twice her son’s age when her daughter is 28 years old. How old will mrs Toh be when her daughter was 20 years old?
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?

[tianzhu]

ozora:

2.when mrs Toh was 40 years old, her son was twice her daughter's age. Mrs Toh would be twice her son's age when her daughter is 28 years old. How old will mrs Toh be when her daughter was 20 years old?

Hi

A similar question was discussed earlier.

Best wishes.

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[tianzhu]

ozora:

1. Don walked from home to school. He was walking at an ave speed of 35m/min for the 1st 5min. He increased his speed by 10m/min when he realized he was going to be late for 4 mins. As a result, he was early by 2 mins. What is the distance bet the school n home?

Hi

Draw a timeline to show the relationships.

Speed ratio ------35:45 ------ 7:9
Time ratio -------9:7

9-7 -----2

2 units ------ 2+4 ------6 min
1 unit ------3 min

7 units ------21

21*45 ------945

5*35 ------ 175

175+945 ------1120

Best wishes

[PiggyLalala]

tianzhu:

ozora:

1. Don walked from home to school. He was walking at an ave speed of 35m/min for the 1st 5min. He increased his speed by 10m/min when he realized he was going to be late for 4 mins. As a result, he was early by 2 mins. What is the distance bet the school n home?

Hi

Draw a timeline to show the relationships.

Speed ratio ------35:45 ------ 7:9
Time ratio -------9:7

9-7 -----2

2 units ------ 2+4 ------6 min
1 unit ------3 min

7 units ------21

21*45 ------945

5*35 ------ 175

175+945 ------1120

Best wishes

Hi tianzhu,
Though my child is not sitting for PSLE this year, I have been reading your solution. I am very touched by the effort and the time you spent in helping to answer the questions almost immediately after the questions have been posted. (Especially so after knowing that you are not a tutor )

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

[tianzhu]

Hi


NY SA2 Q17 2010

It helps to draw a simple diagram.

Scenario 1
At first
Blue --- 3 units + 70
White --- 4 units

Scenario 2
At first
Blue --- 8 parts
White --- 7 parts + 112

8 parts ------ 3 units + 70
7 parts ------4 units -112

Equalise the parts

56 parts ------ 21 units + 490
56 parts ------ 32 units – 896
1 unit ----- 126

Blue marble at first ------ 448 (3 units + 70)
White marbles at first ------ 504 (4 units)

After adding 48 more blue marbles
448+48 ----- 496
Total marbles ------ 496+504 ------1000

496/1000*100 ------49.6%

Best wishes

[ozora]

Thanks tianzhu.

[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

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cheers.