Q&A - PSLE Math

[tianzhu]

Hi Hifive


You're welcome.

If you keen to find out more about Unit Transfer Method, you may refer to this link.
http://www.mathsheuristics.com.sg

This is a good link to find out more about MD.
http://www.aaasurvey.com/tutor_html/bottom_create5_all.html

Best wishes

[Hifive]

Hello tianzhu


Thank you for your advice!

[Belle2011]

Hi,

I need some help again.

(1) Dolly had 80 more stickers than Jenny. Dolly gave 25% of her stickers to Jenny. Jenny in return gave 60% of her stickers to Dolly. In the end, Dolly had 100 stickers more than Jenny. How many stickers did Dolly have at first?

(model ans: 116 stickers)

(2) Julian had 300 more cards than Faizal. Julian gave 3/5 of his cards to Faizal. Faizal then gave 1/4 of the total number of what he had then to Julian. In the end, Faizal had 300 more cards than Julian. How many cards did Julian have at first?

(model ans: 1125)

(3) Tanks X and Y are each filled with some water. If water from Tank Y is poured into Tank X until the water in Tank X reaches the brim, there will be 8 litres of water left in Tank Y. If water from Tank X is poured into Tank Y until the water in Tank Y reaches the brim, there will be 26 litres of water left in Tank X. The ratio of the volume of Tank X to the volume of Tank Y is 5:3. How many more litres of water are needed to fill both tanks to their brim?

(model ans: 19 litres)

Thanking you in advance.

[Brenda10]

Belle2011:

Hi,

I need some help again.

(1) Dolly had 80 more stickers than Jenny. Dolly gave 25% of her stickers to Jenny. Jenny in return gave 60% of her stickers to Dolly. In the end, Dolly had 100 stickers more than Jenny. How many stickers did Dolly have at first?

(model ans: 116 stickers)
Thanking you in advance.

Hi, this question was from Nan Hua 2010 CA1 P2 Q18.

25%= 1/4, 60% = 3/5

1/4=5/20, 3/5 = 12/20
80 x 5/20 = 20, 20 x 12/20 = 12
80 - 20 = 60, 20 - 12 = 8


4u+ 60 + 12 = 100 + 8
4u + 72 = 108
4u = 108 - 72
4u = 36

Dolly: 4u + 80
36 + 80 = 116


Thank you

[Brenda10]

Belle2011:

Hi,

I need some help again.

((2) Julian had 300 more cards than Faizal. Julian gave 3/5 of his cards to Faizal. Faizal then gave 1/4 of the total number of what he had then to Julian. In the end, Faizal had 300 more cards than Julian. How many cards did Julian have at first?

(model ans: 1125)
Thanking you in advance.

Hi, this question was from NY 2010 CA1 P2 Q17.

3/5, 1/4

12/20 , 5/20

300 x 12/20 = 180, 180 x 5/20 = 45
300- 180 = 120, 180 - 45 = 135

2u = 120 + 45 + 300 - 135
2u = 330
1u = 165


Julian: 5u + 300
5 * 165 + 300 = 1125


Thank you

[Brenda10]

Belle2011:

Hi,

I need some help again.

(3) Tanks X and Y are each filled with some water. If water from Tank Y is poured into Tank X until the water in Tank X reaches the brim, there will be 8 litres of water left in Tank Y. If water from Tank X is poured into Tank Y until the water in Tank Y reaches the brim, there will be 26 litres of water left in Tank X. The ratio of the volume of Tank X to the volume of Tank Y is 5:3. How many more litres of water are needed to fill both tanks to their brim?

(model ans: 19 litres)

Thanking you in advance.

Hi, please refer the following link for the info.

http://www.onsponge.com/index.php?option=com_kunena&Itemid=282&func=view&id=1685&catid=35#1685

[Belle2011]

Dear Brenda10,

Thanks very much for your help.

Cheers,
Belle

[Belle2011]

Brenda10:

Belle2011:

Hi,

I need some help again.

(1) Dolly had 80 more stickers than Jenny. Dolly gave 25% of her stickers to Jenny. Jenny in return gave 60% of her stickers to Dolly. In the end, Dolly had 100 stickers more than Jenny. How many stickers did Dolly have at first?

(model ans: 116 stickers)
Thanking you in advance.

Hi, this question was from Nan Hua 2010 CA1 P2 Q18.

25%= 1/4, 60% = 3/5

1/4=5/20, 3/5 = 12/20
80 x 5/20 = 20, 20 x 12/20 = 12
80 - 20 = 60, 20 - 12 = 8


4u+ 60 + 12 = 100 + 8
4u + 72 = 108
4u = 108 - 72
4u = 36

Dolly: 4u + 80
36 + 80 = 116


Thank you

Can anybody offer some detailed explanation?

What does 80-20 = 60, 20-12 = 8 mean?
What does 4u+ 60 + 12 = 100 + 8 mean?
Thanks.

[Belle2011]

Brenda10:

Belle2011:

(2) Julian had 300 more cards than Faizal. Julian gave 3/5 of his cards to Faizal. Faizal then gave 1/4 of the total number of what he had then to Julian. In the end, Faizal had 300 more cards than Julian. How many cards did Julian have at first?

(model ans: 1125)

Hi, this question was from NY 2010 CA1 P2 Q17.

3/5, 1/4

12/20 , 5/20

300 x 12/20 = 180, 180 x 5/20 = 45
300- 180 = 120, 180 - 45 = 135

2u = 120 + 45 + 300 = 135
2u = 330
1u = 165

Julian: 5u + 300
5 * 165 + 300 = 1125

Thank you

Similarly, can anybody offer some detailed explanation?
What does 300- 180 = 120, 180 - 45 = 135 mean?
How to get 2u = 120 + 45 + 300 = 135 ?
Thanks.

[Brenda10]

Belle2011:

Brenda10:

[quote=\"Belle2011\"]
(2) Julian had 300 more cards than Faizal. Julian gave 3/5 of his cards to Faizal. Faizal then gave 1/4 of the total number of what he had then to Julian. In the end, Faizal had 300 more cards than Julian. How many cards did Julian have at first?

(model ans: 1125)

Hi, this question was from NY 2010 CA1 P2 Q17.

3/5, 1/4

12/20 , 5/20

300 x 12/20 = 180, 180 x 5/20 = 45
300- 180 = 120, 180 - 45 = 135

2u = 120 + 45 + 300 - 135
2u = 330
1u = 165

Julian: 5u + 300
5 * 165 + 300 = 1125

Thank you

Similarly, can anybody offer some detailed explanation?
What does 300- 180 = 120, 180 - 45 = 135 mean?
How to get 2u = 120 + 45 + 300 = 135 ?

Thanks.[/quote]Oh there is a typing error, should be:

2u = 120 + 45 + 300 -135

Sorry as I just transferred dd's working and can't help in explanation. Hopefully someone else can help.