Q&A - PSLE Math

[millan]

tianzhu:

millan:

Can u show me in any of the above? thks

Hi

Please go to page 310 of this thread.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&hilit=value+of+money&start=3090

Best wishes

I actually tried using the coin example it comes to a stage where the per unit is in decimal.. abit weird..

[tianzhu]

millan:

[I actually tried using the coin example it comes to a stage where the per unit is in decimal.. abit weird..

Hi

A quick one.

6 $1 notes ------ $6 ------- 30 20cents coins

At first ----- 20cents:$1 ------- 1unit : 4units
Change -----20cents:$1 ------- +30 : -6
In the end --- 20cents:$1 ------- 3 parts : 5parts

Equalising the final parts or cross multiply

5 units + 150 ------ 12 units – 18
7 units ------ 168

1 unit ------ 24

20cents ----- 1 unit ------24*0.2 ------ 4.8

$1 ------- 4 units ------- 96*1 ------96

Hence, total amount is $100.8

You may read up more on Units and Parts by reading Challenging Maths Made Easy by Ammiel Wan.

Best wishes

[pixiedust]

Karen and David had $127 altogether. Karen spent 1/3 of her money on a toy and David spent 3/5 of his money on food. If David spent $9 more than Karen, how much money did Karen have at first ?


I solved using simultaneous equations (from model) and unitary method.
For unitary method, I can get the right answer but I can't explain how to handle the $9.

Appreciate any help with (1) pure model/pictorial solution (2) unitary method with reasoning of how the $9 is handled.
Thanks very much !

[MathIzzzFun]

pixiedust:

Karen and David had $127 altogether. Karen spent 1/3 of her money on a toy and David spent 3/5 of his money on food. If David spent $9 more than Karen, how much money did Karen have at first ?


I solved using simultaneous equations (from model) and unitary method.
For unitary method, I can get the right answer but I can't explain how to handle the $9.

Appreciate any help with (1) pure model/pictorial solution (2) unitary method with reasoning of how the $9 is handled.
Thanks very much !

Hi

this MD should help..

http://i40.tinypic.com/16la521.jpg\">

cheers.

[shin88]

Hi,


Does anyone has the question for Nanyang Ca1 paper 2 Q18 .
The underline part is missing in the exam paper.

The total area of Triangle A and Triangle B is _______ of the area of Triangle C.

Thanks in advance.

[pixiedust]

Thanks MathsIzzzFun ! *banghead* so easy yet I can't see it !


shin88, it is 125%. see here -> http://www.kiasuparents.com/kiasu/forum/viewtopic.php?p=691764#p691764

[tianzhu]

pixiedust:

For unitary method, I can get the right answer but I can't explain how to handle the $9.

Hi pixiedust

Good Morning.

I am wondering what you mean by using unitary method.

The unitary method involves the finding of a value equivalent to one unit. Then use this value to find the value of more units. In a way, the working in MD is quite similar; we are also using the unitary method.

An example of using unitary method.

110% of Science score ------ 88
1% of Science score ----- 88/110
100% of Science score ----- 88/110*100 ----- 80

110 units ------ 88
1 unit ------ 88/110
100 units ----- 88/110*100 ------ 80

Best wishes

[mumworks]

Hi,


Besides using guess and check, any better way to solve this problem ?

360 teachers and pupils participated in tree planting.
Each teacher planted 3 trees and each group of 3 pupils planted 2 trees.
If 520 trees were planted altogether, how many pupils were there ?

Thanks in advance.

[sweetcandy]

mumworks:

Hi,


Besides using guess and check, any better way to solve this problem ?

360 teachers and pupils participated in tree planting.
Each teacher planted 3 trees and each group of 3 pupils planted 2 trees.
If 520 trees were planted altogether, how many pupils were there ?

Thanks in advance.

Hi,

I am not sure if I am right but we can use equation:

360 = T + S (T-teachers and S-Student)
520 = 3T+2S/3 (Total numbers of trees)
.
....

You will get S= 240 (there are 240 students)

Check answer:
240 (students) + 120 Teachers = 360
(240/3)2+(3*120) = 520 trees

So I am not guessing my answer right?

[tianzhu]

mumworks:

Hi,


Besides using guess and check, any better way to solve this problem ?

360 teachers and pupils participated in tree planting.
Each teacher planted 3 trees and each group of 3 pupils planted 2 trees.
If 520 trees were planted altogether, how many pupils were there ?

Thanks in advance.

Hi

You may use \"Make a Supposition\"

This solution for a similar type of question may help.

The answer to your question is 240 pupils (120 teachers)

Best wishes

http://farm8.staticflickr.com/7022/6518324819_548ca9d2dc_z.jpg\">