Q&A - P5 Math

[ariasnow]

Help needed on this. thks


1/8 of the books in the library are Tamil books and 5/24 of them are chinese books. 7/8 of the remaining books are English books. There are 840 English books. Find the total number of books in the library.

[ariasnow]

Help needed. thks.


The cost of 15 notepads and 15 pencils is $37.50. Mr Tan bought 30 notepads, 75 penciles and 30 erasers for $157.50. If 15 Pencils and 15 erasers cost $31.50, find the cost of 1 eraser.

[tianzhu]

ariasnow:

Another question:


Sam had 20 more cards than Tony. During a game, Tony lost 14 of his cards to Sam. In the end, Sam had 4 times the number of cards that Tony had. How many cards did Sam have at first?

Hi

Hope this helps.

Best wishes.

http://farm8.staticflickr.com/7200/6991827451_f8db9baf6e_z.jpg\">

[tianzhu]

ariasnow:

Pls help with the above questions with thanks.


Another question,

Wendy had $230 and Mary had $38. When their mother gave them each an equal amt of money, Wendy had 4 times as much as Mary. How much did their father give EACH of them?

Hi

Since their mothers gave each of them an equal amount of money, the difference in amount of money between Wendy and Mary stayed the same at (230-38) which was 192.

Wendy ------ 4 units

Mary ------ 1 unit
3 units ------ 192

1 unit ------ 64
64 – 38 ------ 26

Their mother gave each of them $26.

Best wishes

[buds]

Gemini11:

Hope it helps. Gemini11 :evil:

Hi Gemini! Thanks! :please:
Yes, it was very helpful.

While i usually very much look forward to tianzhu's beautiful model drawings and workings, yours were pleasantly simple to comprehend and tongue in cheek some more. I loike too!

DD says thank you very much and had used your workings in her worksheets.

Gemini11:

PS: Sorry tianzhu hope you dont mind i hijacked your questions.

The more the merrier. So we can all choose from a variety of solutions from the many knowledgable parents here in the forum. There's always more than one way to reach the correct answer. Our kiddies are spoilt for choice. They can use the one solution they can understand the best. :celebrate:

[buds]

MathIzzzFun:

http://i42.tinypic.com/35mo390.jpg\">

MathIzzFun, thank you so much for the alternative solutions! :please:

Appreciate it a lot.

[buds]

cimman:

buds:

I am thinking of a fraction.
The sum of its numerator and denominator is 20.
When i add 22 to its denominator, the fraction becomes 1/6.
What is the fraction i am thinking of?

I've recently developed a way to solve problem sums with algebra and simultaneous equations. It offers a simple way of forming the necessary equations. For the above problem, it is an equation with one unknown.
http://i40.tinypic.com/3347uxs.png\">
The fonts in black are values transferred directly from the problem to the table. The fonts in red are calculated values.
The calculation is based on this basic formula: Before + Transfer = After
how did I get (6 units - 22) for Denominator (Before) ?
it is from Before = After - Transfer
= 6 units - (+22)
= 6 units - 22
Since there was no mention of any changes to the Numerator, we put a 0 in the Transfer box for numerator.

The red circle simply circles the relevant equation.
All equations are dervied directly from the table.

If you're open to algebra and simultaneous equations, this method can solve complex problems easily, ie. the equations can be formed easily through the table alone. From the table, the relationships can be clearly seen without a deep comprehension of the problem sum and the relationships of the data values.
The relationships are derived from the table instead of from the problem sum.

Wow! You developed this transfer solution yourself? :salute:
I loike it! :love: Nice to see different ways to come to the same answer.
Looking at the different perspectives from everyone who has shared just shows
that Math isn't that impossible to comprehend.

[YumYum]

tianzhu:

YumYum:

Hi, Can someone pls help with this question:


Farmer Tan has ducks and cows on his farm. The total number of ducks and cows is between 20 and 40. The ratio of the total number of ducks' legs to the total number of cows' legs is 5:9. What is the total number of ducks and cows on the farm?

Thanks

Hi

One needs to differentiate the ratios representing the number of legs and the number of animals. The ratios for the number of legs and the number of animals are of different measures.

The total number of ducks' legs to the total number of cows' legs is 5:9 ------ 20:36 (equivalent ratios)

A duck ----- 2 legs, a cow ----- 4 legs

This means the total number of ducks to the total number of cows ----- 10:9 -----20:18

Ducks ----- 20
Cows ----- 18

There are 38 ducks and cows.

Best wishes

thank you

[metz]

buds:

Helloooo again, tianzhu! :peekaboo:


I have a few more for you here.

I am thinking of a fraction.
The sum of its numerator and denominator is 20.
When i add 22 to its denominator, the fraction becomes 1/6.
What is the fraction i am thinking of?

This question carries 4 marks! :yikes:

Once your dd learns Ratio, it might be easier for her to solve such questions.

ratio of numerator to denominator after adding 22 to denominator = 1:6
New total = 20+22 =42
(Total units = 1 + 6 = 7)
7 units -> 42
1 unit -> 6
nominator = 6
Denominator = 36 - 22 = 14
fraction = 6/14

[cimman]

buds:

Wow! You developed this transfer solution yourself? :salute:
I loike it! :love: Nice to see different ways to come to the same answer.
Looking at the different perspectives from everyone who has shared just shows
that Math isn't that impossible to comprehend.

if you're interested in this technique, I'm conducting a workshop to teach parents on how this technique works.

The same technique works on problems like these:
1.\tJohn and Sherry shared some sweets. John has 180 sweets less than Sherry. If Sherry gives 1/7 of her share to John, John will have 20 more sweets than Sherry How many sweets did Sherry have at first? Ans: 700

2.\tDoris and Annie have each planned a list of words to learn. If Doris learnt 40 words per day while Annie learnt 20 words per day, Doris would have 70 words left to learn while Annie had completed learned all the words. If Doris learnt 20 words per day while Annie learnt 40 words per day, Doris would have 130 words left to learn while Annie had completed learned all the words. How many words do Doris and Annie have to learn respectively? Ans: Doris:150, Annie: 40

This technique works, because all Transfer type problems are bounded by this very simple equation:
Before + Transfer = After
...... and thus, we can make use of that very fact to solve all Transfer Type problems. A Transfer Type problem is defined by a problem in which some value is decreased or increased or both. This covers a very wide range of problems in PSLE Maths.

There's no need to use different techniques for different problem patterns. It makes it a lot easier for a child to understand and drill on just one method.

My child would find it difficult to identify unchanged total or unchanged difference or unchange quantity in a problem. This method was created to remove that layer of linguistic inference of problem sums.

I created a thread in the Happenings forum.
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=43&t=32278
You can register for the next workshop. Just drop me a PM and I'll alert you on the next workshop date.