Q&A - PSLE Math

[tianzhu]

whitety:

Hi, need help on this qn.


In a bag, there are 20-cent and 50-cent coins. There are 28 more 20-cent coins than 50-cent coins but the total amount of 50-cent coins is $3.40 more than that of the total amount of 20-cent coins. How many 50-cent coins are there in the bag?

Thanks!

Hi

Please study this solution for a similar type of question.It should help to answer your question.

Best wishes

http://farm6.staticflickr.com/5014/5557734869_1bdc3c4e23_z.jpg\">

[Zhu99]

tianzhu:

zanen:

in a test of fuel consumption, two cars, P and Q, each travel a distance of 720km.

For every litre of petrol used, Car Q travels 3km more than Car P.
Car P uses 12 litres of petrol more than Car Q.
Find the number of litres of petrol each car has used for the journey.
please help me as i am taking retake prelim tmr. thanks

Hi

I am sorry; the solution is not within your expected schedule.

Please do allow reasonable time for your questions to be answered as those answering questions are volunteers who can only do them in their spare time.

This is a very interesting question. It is crafted in such a way that it can be neatly solved by GC.

I’ll leave it to you to do the presentation for the GC.

The answers are 60 (60*12) and 48(48*15).

15 ------ 3 more than 12

60 ------- 12 more than 48

Hence, the conditions are met.

Best wishes

P: 1 litre -- 1 u km
Q: 1 litre -- 1 u + 3 km

(1 u x m) + 12 u ---> 720 km ------ P uses (m + 3) litres
(1 u + 3) x m ---> 720 km -------- Q uses m litres (m times)

(1 u x m) + 12 u --> (1 u x m) + (3 x m)
1 m --> 12 u / 3 = 4 u

(1 u x 4 u) + 12 u ---> 720
Using calculator, trial and error, 1 u ---> 12

Check and confirm
(12 x 48) + 12 x 12 --->720
(12 + 3) x (4 x 12) ---> 720

1m ---> 4 x 12 = 48 litres

48 + 12 = 60 litres

So P uses 60 litres while Q uses 48 litres.

[tianzhu]

altp10:

http://i45.tinypic.com/2vbrbdf.jpg\">


Hi. Can someone help me out with this question please?

Thank u in advance.

Hi

I don’t have time to prepare a more colourful slide.

This basic idea is to have proper zonings.

Hope this is good enough for you.

Best wishes

http://farm9.staticflickr.com/8319/7935008548_65a59e6ecf_z.jpg\">

[tianzhu]

zanen:

Containers A and B are each filled with water.If the water from container B is poured into container A until container A reaches the brim, there wil be 12 litres of water left in container B. If the water from container A is poured into container B until container B reaches tbe brim, there will be 34 litres of water left in container A. The ratio of the capacity of container A to the capacity of container B is 2:1. How many more litres of water are needed to fill both tanks to their brim? please help thanks. my prelim retest tmr.

Hi

There are two possible scenarios and it’s important that students can see that the volume of water stays the same before and after.

Depending on one's preference, you may use MD or use units.Due to time constraints, I'll skip the slide this time round.

If the water from container B is poured into container A until container A reaches the brim, there wil be 12 litres of water left in container B.

Volume of water ----- 2 units + 12

If the water from container A is poured into container B until container B reaches tbe brim, there will be 34 litres of water left in container A.

Volume of water ----- 1 unit + 34

2 units + 12 ------ 1 unit + 34

1 unit ----- 22

Total volume of water in both tanks ------- 3 units ------- 66

Volume of water at present ------- 2 units + 12 ------ 56

Hence, you need 10 litres more.

Best wishes

[tianzhu]

2DMommy:

1) Paris had a total of 1686 red, blue, green marbles for sales. The ratio of the number of red marbles to the number of blue marbles is 2:3. After Paris sold 75% of the blue marbles and 50% of the green marbles and none of the red marbles, she had 922 marbles left. How many blue marbles were there at first ?

Hi

You may want to draw a simple diagram if you need one.

Red:Blue ------ 2:3 ------ 8:12

Sold

Red ------ none

Blue ------ 9 units

Green ------ 1 part

Left

Red ------ 8 units

Blue ------ 3 units

Green ------ 1 part

11 units + 1 part ------ 922

9 units + 1 part ------ 764

2 units ------ 158

1 unit ------ 79

Number of blue marbles@first ------- 12*79 ------- 948

Best wishes

[whitety]

tianzhu:

whitety:

Hi, need help on this qn.


In a bag, there are 20-cent and 50-cent coins. There are 28 more 20-cent coins than 50-cent coins but the total amount of 50-cent coins is $3.40 more than that of the total amount of 20-cent coins. How many 50-cent coins are there in the bag?

Thanks!

Hi

Please study this solution for a similar type of question.It should help to answer your question.

Best wishes

http://farm6.staticflickr.com/5014/5557734869_1bdc3c4e23_z.jpg\">

:thankyou: Tianzhu for the example given.

[Zhu99]

mn:

Hi I need help on this question. Please help, thanks in advance.

Miss Lee baked some pies to sell at a fun fair. 4/5 of them were beef pies while the rest were chicken pies. At the end of the fun fair, she sold 100 chicken pies and 7/8 of the beef pies. 1/6 of the pies remained unsold. If each pie cost $2.50, how much did Miss Lee collect from the sale of the pies?

B [ ][ ][ ][ ][ ][ ][ ][ ]
C [ ][ ]
100

1/6 x 10 u = 1 2/3 u

1 2/3 u - 1 u --> 2/3 u [C unsold]

2 u - 2/3 u = 1 1/3 u ---> 100 [C sold]
1 u ---> 100 x 3/4 = 75

7 u ---> 7 x 75 = 525

525 + 100 = 625

625 x 2.50 = $1562.50

She collected $1562.50.

[jonaandr]

Please help to solve the below questions.


1. Richard drove Cindy from Village X to Village Y at a constant speed of 60km/h.
From Village Y, Cindy walked 7km to Village Z at a speed of 4km/h.
From Village Y, Richard turned back to Village X to pick James up.
He drove along the same route at a constant speed of 60km/h to meet Cindy
at Village Z.
They reached Village Z at the same time.
Find the distance beween Village X and Village Z.

2. There were 124 adults in a hall. When 5/8 of the men and 4/7 of the women left the hall, the total number of men and women who remained became 48. How many men were there in the hall at first?

3. Katy had a number of 20-cent coins and Jeremy had a number of 50-cent coins. Katy had 18 more coins than Jeremy but Jeremy had $8.10 more than Katy. express, to the nearest percent, the amount of money Katy had as a percentage of the amount of money Jeremy had.

4.alicia and Bruce are given some money each. If Alicia spends three times as much as Bruce,She will have $1000 more when Bruce has spent all his money. If alicia spends half of what Bruce spends, she will have $2200 when Bruce has spent all his money. What is the total sum of money given to Alicia and Bruce?

Thanks!

[altp10]

tianzhu:

altp10:

http://i45.tinypic.com/2vbrbdf.jpg\">


Hi. Can someone help me out with this question please?

Thank u in advance.

Hi

I don’t have time to prepare a more colourful slide.

This basic idea is to have proper zonings.

Hope this is good enough for you.

Best wishes

http://farm9.staticflickr.com/8319/7935008548_65a59e6ecf_z.jpg\">

Thanks alot tianzhu. I had managed to get E+G=228 but didn't know if it was right. Now after your zoning, I can see how you dissected the figure to get the difference between E & F. I was also trying to work my way to get F but thought how is it possible when P6 haven't even learn Trigonometry.

Cheers..

[tianzhu]

altp10:

Thanks alot tianzhu. I had managed to get E+G=228 but didn't know if it was right. Now after your zoning, I can see how you dissected the figure to get the difference between E & F. I was also trying to work my way to get F but thought how is it possible when P6 haven't even learn Trigonometry.

Cheers..

Hi

You’re welcome.

No trigonometry has been used. All is within the syllabus.

First find the difference of E+G-F, then take away G ( the area of the semi circle G).

228 ----- E + G - F, not E + G

Best wishes