Q&A - PSLE Math

[Amberz]

The total of 4 numbers P, Q, R,and S was 291.

When P was tripled, Q was halved, R was increased by 20 and S was decreased by 25, the four numbers became equal.
Find the value of R. :?

[iFruit]

pixiedust:

Hi all, I am completely :stupid: with CA1 revision.

I would greatly appreciate help with the following :

Q2:
We have the answer and solution for this question but I need the systematic way to approach such question so that if the number changes, we can still find the solution. Basically :
(a) how to find the number of pairings ?
(b) how to determine if there is a middle no partner number ? how to find it ?

I think it'd be useful to remember the following formula ( and be able to apply, of course).

nth term = 1st term + (n-1)d where n = number of terms, d = common diff.

Sum of n terms = (1st term + last term)n/2

Once you find n, you can just find the middle term from n/2, but usually it is not necessary if one remembers the above formulae.

Just my POV.

[iFruit]

Amberz:

The total of 4 numbers P, Q, R,and S was 291.

When P was tripled, Q was halved, R was increased by 20 and S was decreased by 25, the four numbers became equal.
Find the value of R. :?

This is a backwards problem..

Assume at the end, each number became 3u.

Then at the beginning:

P = 3u/3 = u
Q = 3u x 2 = 6u
R = 3u - 20
S = 3u + 25

u+6u+3u-20 + 3u + 25 = 291

13u = 286--->u =22

R = 3u - 20 = 46

HTH.

[tianzhu]

youngtay:

Hi, please help


Mrs Goh sells mooncakes in boxes of twos and fours. At first, there were four times as many small boxes as bog boxes. After selling half the number of small boxes and some big boxes, Mrs Goh packs 5 more boxes of mooncakes. Given that there are thrice as many small boxes as bIg boxes and there is a total of 300 mooncakes in the unsold boxes, find the number of big boxes sold. (Ans given 20 - A* maths)


TIA

Hi youngtay

Due to time constraints, I’ll give you some pointers instead of MD.

In answering this question, a student should recognise that the before and after ratios are of different kinds. The before ratios represent number of boxes of moon cakes and the after ratios represent value or the number of moon cakes.

You may use MD or UM to solve it.

In the end, here we are talking about number of unsold moon cakes.

Small boxes ------ 6 units
Big boxes ------- 4 units

10 units ------- 300
1 unit -------30

Number of unsold moon cakes in small boxes --------6*30 -------180
Number of unsold small boxes of moon cakes --------180/2 ------90
Number of unsold moon cakes in big boxes --------4*30 -------120
Number of unsold big boxes of moon cakes --------120/4 ------30

At first, here we are talking about number of boxes.

Number of moon cakes in small boxes ---------90*2 --------180
Number of moon cakes in big boxes ---------180*4 --------45

Next, find the number of big boxes sold.

30 - 5 ----- 25
45 – 25 -----20

Best wishes

[anneshirleygilbert]

tianzhu:

anneshirleygilbert:

With the use of the calculator, I took about 9 minutes to get to arrive at the answer. Is this too long to spend on a 4 or 5 marks question in the PSLE? Pls advise.

Hi anneshirleygilbert

I am sorry; I am not in a position to answer your question this time.

I believe the school teachers would have taught the students time management.

Your kid’s teacher would be in a better position to advise you.

Perhaps, you may find something interesting in this article.

http://www.epopular.com.sg/my-kid/100-for-maths-yes-you-can.php

Best wishes

Thank you for the link, tianzhu. You are so resourceful. The articles are enlightening and helpful.

[tianzhu]

anneshirleygilbert:

Thank you for the link, tianzhu. You are so resourceful. The articles are enlightening and helpful.

Hi anneshirleygilbert

You're welcome.

Best wishes

[rossypolly]

I’m stuck with this question. Hope someone can help me out with this one.


Justin baked some pies. 1/3 of the pies were chicken pies & the rest were vegetable pies. He packed 3/4 of the vegetable pies into big boxes & the rest of the vegetable pies into small boxes. each big box of vegetable pies made up 1/12 of the total no. of pies. Each small box of vegetable pies made up 1/16 of the total no of pies.

How many big boxes of vegetable pies were there?

How many small boxes of vegetable pies were there?

[rossypolly]

I’m stuck with this question. Hope someone can help me out with this one.


Justin baked some pies. 1/3 of the pies were chicken pies & the rest were vegetable pies. He packed 3/4 of the vegetable pies into big boxes & the rest of the vegetable pies into small boxes. each big box of vegetable pies made up 1/12 of the total no. of pies. Each small box of vegetable pies made up 1/16 of the total no of pies.

How many big boxes of vegetable pies were there?

How many small boxes of vegetable pies were there?

[Puffer]

Can anyone help?


In planning for a party, Mrs Lim bought enough satay to allow her guests an average of 25 sticks each. If 2 more people joined the party, how many fewer sticks of satay will each of her guests be given?

Thanks in advance.

[tianzhu]

Puffer:

Can anyone help?


In planning for a party, Mrs Lim bought enough satay to allow her guests an average of 25 sticks each. If 2 more people joined the party, how many fewer sticks of satay will each of her guests be given?

Thanks in advance.

Hi

Good Afternoon.

I did a quick check; it looks like there are multiple answers.

One is 10 and the other is 5.

It is suggested that you use Tabulated list/Systematic listing to solve this question.

Best wishes