Q&A - P5 Math

[Jcong]

Pail A contained 7/17 of the amount of water in Pail B. Pail C contained 1/9 of the total amount of water the three pails had. If Pail A and Pail B contained 5.25 litres of water more than Pail C, how much water did Pail B contain? (give the answer in litres)

[tianzhu]

Jcong:

Pail A contained 7/17 of the amount of water in Pail B. Pail C contained 1/9 of the total amount of water the three pails had. If Pail A and Pail B contained 5.25 litres of water more than Pail C, how much water did Pail B contain? (give the answer in litres)

Hi

Pail A ----- 7 units

Pail B ----- 17 units

Multiples of 9 ------- 9, 18,27 ………

1/9*27 -----3 units

Pail C ------ 3 units.

24units – 3 units ------ 21units

21units ----- 5.25

1unit ----- 0.25

Pail B -----17*0.25 ------- 4.25

Best wishes

[Jcong]

Why do you use multiple of 9? and why is 27 chosen instead of other numbers like 18? So sorry don’t really understand. Thanks

[tianzhu]

Jcong:

Why do you use multiple of 9? and why is 27 chosen instead of other numbers like 18? So sorry don't really understand. Thanks

Hi

C contained 1/9 of the total amount of water the three pails had.
Hence, we use multiples of 9, just to make the calculations easier.

The number of units for Pail A and Pail B add up to 24(7+17).

Hence the total number of units(A+B+C) has to be greater than 24.

Alternatively, you may use MD.

7units (Pail A) +17units (Pail B) + 1part (Pail C) ------- 9 parts (representing A+B+C)

24units ------- 8parts

3units ------- 1part.

Best wishes

[Jcong]

Thank you so much. Now I understand.

[tianzhu]

Jcong:

Thank you so much. Now I understand.

Hi

Good Morning.

You’re welcome.

Best wishes

[pixiedust]

Hi all, please help me the following:


Source : 2010 RGPS P5 SA2
http://orlesson.com/10Ma/2010-P5-Math-SA2-RGPS.pdf

Paper 1, Question 28.
Paper 1, Question 29.

Paper 2, Question 12. Part (a) My answer is $319.50 which is different from answer key.
Paper 2, Question 17.

Thanks in advance.

[tianzhu]

Hi


Hope this helps.

Best wishes.

http://farm7.static.flickr.com/6205/6122997729_9ce9c915f3_z.jpg\">

[tianzhu]

Hi


For P2 Q17

Part (a) is a gift, the answer is 140cm.

For part (b)

A:B ------- 80:140 -------4:7
Common multiple ------- 28

So you can get 7 pieces of A and 4 pieces of B.

A means plank in figure A (80) and B means plank in figure B (140)

Consider 1 set of A and B

Number of circular stickers ----- 74 -----28

Number of triangular stickers ------ 49 ------36

Total number of stickers ------64

There are (36-28) or 8 more triangular stickers than circular stickers in one set.

136/8 ----- 17

17*64 ------1088.

If you need the slides, please let me know.

Best wishes.

[PiggyLalala]

tianzhu:

Hi


Hope this helps.

Best wishes.

http://farm7.static.flickr.com/6205/6122997729_9ce9c915f3_z.jpg\">

:thankyou: for the solution.
Q28 is really a tough one. I was about to use similar triangles ( which is not in the primary school syllabus) to find the area.

Questions on area can be quite tough. Any techniques/advice/steps for the pupils to think through when solving challenging area questions? Thanks