Q&A - PSLE Math

[altp10]

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

Thank u in advance.

[ruohoo97]

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?

Beef Pie: Chicken Pie-----Total

8/10 2/10 10/10
Sold 7/10 100 1/6

1/10*x+1/5*x-100=1/6*x

x=75
Total money collected:75x2.5=$187.5

[ruohoo97]

2DMommy:

Please help me with these questions :


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 ?

2) If Sam gives Terry $350, he will have 4 times as much money as Terry. If Sam gives Terry $550, he will have thrice as much money as Terry. How much money does Sam have ?

Thank you !

For question 2)
Is that okay to use algebra,

4(T+350)=S-350
3(T+550)=S-550

T=450; S=3200

[charsen]

zanen:

A car and a lorry were travelling towards Sunshine Park. When the car overtook the lorry, they were 260km away from Sunshine Park. The car arrived at Sunshine Park 2.5h earlier than the lorry. When the car reached Sunshine Park, the lorry was still 100km away. Find the speed of the car and the lorry.please help thanks. my prelim retest tmr.

Hi
You can find the speed of the lorry easily.
100/2.5=40km/h(ANS)

260/40=6 1/2h
6 1/2- 2 1/2 =4h
4h--->260
car's speed---->260/4=65km/h(ANS)
cheers

[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

[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

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[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:

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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