Q&A - PSLE Math

[tianzhu]

In this question, you’ll see that the ratios are comparing the quantity or number of notes and not the value of notes. Angel exchanged 12 pieces of $100 into some $5 notes. Hence, the number of notes in the before and after scenarios is different.


Some students may recognise that the value or amount of money remains the same and may prefer to work using the concept of unchanged total quantities.

There are a few ways to solve this question, Units Method, MD or Systematic listing.

Hope this helps

Best wishes

http://farm6.static.flickr.com/5019/5444329416_183f66d5eb_b.jpg\">

[kay22]

JSSK:

Dear bro/ sis,


Can anyone help me with following maths problems? Thanks a million.

Mt. Tan puts up poles from one end of a road to the other at equal distances apart.There are 27 wooden poles. The width of each pole is 10 cm. The distance between 2 poles is 30m. Find the length of the road.

9) Krishnan had 64 coins in his coin box.There were 20-cent coins and 50-cent coins. The total value of all coins was $18.50. How many 20-cent coins and how many 50 cent coins were there?

10) Daisy, Lily & Florence share $268. Lily has $20 more than Daisy and Florence has twice as much as Lily. How much money do Daisy & lily have altogether?

11) Xuxian and Rachel had the same number of marbles. After Rachel gave away 10 marbles and Xuxian gave away 22 marbles, Rachel had 3 times as many marbles as Xuxian. How many marbles did each of them have at first?

12) Gerry had a total of 30 pens and pencils at first. He then decided to exchange all his pens for pencils. If he exchanged every pen for 2 pencils, he would have 48 pencils. How many pens & pencils did he have at first?

5) A carton can hold 850cm3 of grape juice. Grace wants to buy 15 such cartons of grape juice. Every 250cm3 of grape juice costs $1. How much does she have to pay altogether?

6) A sweet cost 15 cents and a packet of 8 similar sweets cost 1. Clement bought exactly 37 sweets. What was the least amount of money that Clement spent on sweets?

Hi hi, can I know which school qns are that as my daughter has the same questions as you too?

[Brenda10]

tianzhu:

In this question, you’ll see that the ratios are comparing the quantity or number of notes and not the value of notes. Angel exchanged 12 pieces of $100 into some $5 notes. Hence, the number of notes in the before and after scenarios is different.


Some students may recognise that the value or amount of money remains the same and may prefer to work using the concept of unchanged total quantities.

There are a few ways to solve this question, Units Method, MD or Systematic listing.

Hope this helps

Best wishes

http://farm6.static.flickr.com/5019/5444329416_183f66d5eb_b.jpg\">

Hi Tianzhu

Thank you for making the presentation so attractive.

BTW, I notice dd prefers to use the units method to the other two methods.

Wish you a nice day.

[Belle2011]

Dear tianzhu,

Thanks very much for your solution.

Can you please help if my working is correct?
$100 : $5 is 7:4.
Generate the equivalent ratios, we will have 14:8, 21:12, 28:16, …etc
The total amount of money involved remains the same before and after the exchange.

For 14:8, if we minus 12 from 14, we have 2. (12 is due to 12 pieces of $100).
If we add 240 to 8, we get 248. (240 is due to 240 pieces of $5).
But 2:248 can’t be reduced to the required final ratio 1:16.

Similarly for 21:12.

For 28:16, if we minus 12 from 28, we have 16, if we add 240 to 16, we get 256. AND 16: 256 = 1:16.

Thus 28:16 is the right ratio, which means we have 28 pieces of $100 and 16 pieces of $5.

This worked out to be $2880.

Thanks.

Cheers,
Belle.

[Leanne]

Hi Tianzhu,


Really loves all the beautiful model that u have drawn.It makes math so much interesting.

Cheers
Leanne

Brenda10:

tianzhu:

In this question, you’ll see that the ratios are comparing the quantity or number of notes and not the value of notes. Angel exchanged 12 pieces of $100 into some $5 notes. Hence, the number of notes in the before and after scenarios is different.

Some students may recognise that the value or amount of money remains the same and may prefer to work using the concept of unchanged total quantities.

There are a few ways to solve this question, Units Method, MD or Systematic listing.

Hope this helps

Best wishes

http://farm6.static.flickr.com/5019/5444329416_183f66d5eb_b.jpg\">

Hi Tianzhu

Thank you for making the presentation so attractive.

BTW, I notice dd prefers to use the units method to the other two methods.

Wish you a nice day.

[tianzhu]

Hi Belle


I observe you are trying to do this question with listing and GC.You may use such method provided you are clear with the concept you want to apply prior to the solution.

If this question were to appear in an examination, it would likely to be in the 4/5 marks category. Hence, neat presentation is essential to secure good marks.

If you prefer to use the Systematic listing, may I suggest you do it in a tabulated form. Depending on the question, this method may be time consuming. You need to apply knowledge on equivalent ratios, addition and subtraction.

Like I said earlier, some students may prefer to work on the basis of unchanged total value of money. There are two ways to go about doing this.

The first way is to convert the ratios representing number in ratios showing value, then using Units Method or MD to solve the question.
The second way is shown in My Pals P6 Volume 2, if I remember it correctly. (Note, I am referring to the old edition, please check the latest edition).

However, for your question, as the ratios are given to represent numbers, it’s more appropriate rely on the concept of Two changed quantities or Total changed. The Units Method, in my opinion, is appropriate for such question.

Best wishes

PS — I am a parent, what I am sharing with you is my experience in my journey with my kid in PSLE Maths.

[tianzhu]

Leanne:

Hi Tianzhu,


Really loves all the beautiful model that u have drawn.It makes math so much interesting.

Cheers
Leanne

Brenda10:

Hi Tianzhu

Thank you for making the presentation so attractive.

BTW, I notice dd prefers to use the units method to the other two methods.

Wish you a nice day.

Hi Leanne and Brenda10

I am happy you liked it.

Brenda10 --- Yes, sometimes, Units Method may be a better alternative to MD for some types of question.
We learned it two years ago from Challenging Maths Made Easy. Yes, my kid simply loved it.

Best wishes

[JSSK]

Xishan Pri School : ) Btw,my son has already solved the problems

kay22:

JSSK:

Dear bro/ sis,

Can anyone help me with following maths problems? Thanks a million.

Mt. Tan puts up poles from one end of a road to the other at equal distances apart.There are 27 wooden poles. The width of each pole is 10 cm. The distance between 2 poles is 30m. Find the length of the road.

9) Krishnan had 64 coins in his coin box.There were 20-cent coins and 50-cent coins. The total value of all coins was $18.50. How many 20-cent coins and how many 50 cent coins were there?

10) Daisy, Lily & Florence share $268. Lily has $20 more than Daisy and Florence has twice as much as Lily. How much money do Daisy & lily have altogether?

11) Xuxian and Rachel had the same number of marbles. After Rachel gave away 10 marbles and Xuxian gave away 22 marbles, Rachel had 3 times as many marbles as Xuxian. How many marbles did each of them have at first?

12) Gerry had a total of 30 pens and pencils at first. He then decided to exchange all his pens for pencils. If he exchanged every pen for 2 pencils, he would have 48 pencils. How many pens & pencils did he have at first?

5) A carton can hold 850cm3 of grape juice. Grace wants to buy 15 such cartons of grape juice. Every 250cm3 of grape juice costs $1. How much does she have to pay altogether?

6) A sweet cost 15 cents and a packet of 8 similar sweets cost 1. Clement bought exactly 37 sweets. What was the least amount of money that Clement spent on sweets?

Hi hi, can I know which school qns are that as my daughter has the same questions as you too?

[tianzhu]

Hi Belle2011


Good Morning

Here's one way to solve your question if you prefer to use the concept of unchanged total value.

Hope this helps.

Best wishes.

http://farm5.static.flickr.com/4149/5446722398_7a9141f966_b.jpg\">

[anneshirleygilbert]

Hello tianzhu,


I was attracted by your colourful presentation on the ratio question about Angel exchanging the $100 notes to $5. I follow your steps but have a question about the method where you make the ending ratio the same. Why do you need to make the ending ratio the same number of units?

Thank you in advance.