Q&A - PSLE Math

[dazzlego]

Hi lee tong fong,


A:C = 125:100 = 5:4 (the one after the word than is always 100%)
C:B = 160:100 = 8:5
So A:B:C = 10:5:8 and A:B = 2:1

Rephrasing the questions to:
At first, A had 2 units and B has 1 unit. A lost 3 parts and B lost 1 part of their cards to C.
2u - 3p = 780
1u - 1p = 480

2u - 2p = 480 x 2 = 960
1p = 960 - 780 = 180
1u = 180 + 480 = 660
A: 2u = 660 x 2 = 1320

Cheers :celebrate:

lee tong fong:

Can you please help to solve another 2 more problem sum, thanks in advance

2) Azman had 25% more marbles than chongfu. Chongfu has 60% more marbles than Bala. During a game, Azman and Bala lost some marbles to Chongfu in the ratio 3:1 . In the end, Azman and Bala had 780 and 480 marble left respectively. How many marbles did Azamn have at first?

[lee tong fong]

Thanks for your answer and is it possible to use model instead of simultaneous equation to work out the solution.Thanks


2u - 3p = 780
1u - 1p = 480

2u - 2p = 480 x 2 = 960
1p = 960 - 780 = 180
1u = 180 + 480 = 660
A: 2u = 660 x 2 = 1320

[dazzlego]

lee tong fong:

Thanks for your answer and is it possible to use model instead of simultaneous equation to work out the solution.Thanks


2u - 3p = 780
1u - 1p = 480

2u - 2p = 480 x 2 = 960
1p = 960 - 780 = 180
1u = 180 + 480 = 660
A: 2u = 660 x 2 = 1320

Yes, it is possible. However since P6 students have already learned how to solve simultaneous equations, it's better to use it. This approach is less time consumed too.

Model:
2u = 3p + 780
1u = 1p + 480

http://i48.tinypic.com/21n2m49.jpg\">

1p = 480 + 480 - 780 = 180

[lee tong fong]

Got it ! Thanks for your time to draw the model.

[lee tong fong]

I have a new problem sum. Please help me to solve. Thanks in advance.


Joyce gave $480 of her monthly salary to her mother. She gave 30% of the reminder to her father. Althogether, she gave 58% of her monthly salary to her father and mother. She saved 20% of her monthly salary.
(a) What percentage of her monthly salary did she give to her father?
(b) How much did she save?

[Maths Hub]

lee tong fong:

I have a new problem sum. Please help me to solve. Thanks in advance.


Joyce gave $480 of her monthly salary to her mother. She gave 30% of the reminder to her father. Althogether, she gave 58% of her monthly salary to her father and mother. She saved 20% of her monthly salary.
(a) What percentage of her monthly salary did she give to her father?
(b) How much did she save?

First of all, we have to be clear that out of her salary, 20% is saved, 58% is given to parents, and 22% is for other purposes. The 22% and 20% of her salary will add up to the 70% of the remainder after giving to her mother.

Let her salary be 100 units. The amount that she saved is 20 units, the amount she gave her father and mother will be 58 units and 70% of the remainder will be 42 units.

70% of remainder-> 42 units
100% of remainder-> 42X10/7=60 units
Therefore 100 units - 60 units= 40 units is given to her mother and 58 units - 40 units = 18 units is given to her father.

a) 18 units/100 units = 18%
b) 40 units ->$480
1 unit -> $12
20 units ->$240

[MathIzzzFun]

lee tong fong:

I have a new problem sum. Please help me to solve. Thanks in advance.


Joyce gave $480 of her monthly salary to her mother. She gave 30% of the reminder to her father. Althogether, she gave 58% of her monthly salary to her father and mother. She saved 20% of her monthly salary.
(a) What percentage of her monthly salary did she give to her father?
(b) How much did she save?

..equal fraction approach ...

$480 + remainder = total salary

58% of salary given to father and mother
so,
$480 (mother) + 30% of remainder = 58% of salary
amount left:
70% of remainder = 42% of salary .... equal fraction
70/100 of remainder = 42/100 of salary
remainder = 6/10 of salary
$480 (mother) --> 4/10 of salary = 40% of salary
percentage of salary given to father = 58% - 40% = 18% of salary (a)

40% of salary --> $480
20% of salary --> $240 -- she saved $240 (b)

cheers.

[lee tong fong]

Thanks for your detail working solution. It is difficult to explain to kid the equal fraction concept


70% of remainder = 42% of salary … equal fraction
70/100 of remainder = 42/100 of salary
remainder = 6/10 of salary

Is there any simplify way to do so . Thanks

[StaryNight]

lee tong fong:

Thanks for your detail working solution. It is difficult to explain to kid the equal fraction concept


70% of remainder = 42% of salary .... equal fraction
70/100 of remainder = 42/100 of salary
remainder = 6/10 of salary

Is there any simplify way to do so . Thanks

Hi lee tong fong,
maybe you could do it using ratio
70/100 Remainder = 42/100 Salary
7/10 Remainder = 21/50 Salary
make the numerator (top number of fraction) the same
21/30 Remainder = 21/50 Salary

now make it into a ratio

Remainder: Salary
30 : 50
=3 : 5

then the rest should be ok

5u-3u=2u
2u--> 480
1u--> 480/2= 240
5u--> 240*5=1200
20% of 1200 = 20/100*1200=240

Hope this helps!

[Maths Hub]

lee tong fong:

Thanks for your detail working solution. It is difficult to explain to kid the equal fraction concept


70% of remainder = 42% of salary .... equal fraction
70/100 of remainder = 42/100 of salary
remainder = 6/10 of salary

Is there any simplify way to do so . Thanks

Referring to the method I showed earlier, we use 100 units for 100% of salary as some children find it hard to understand percentage equals to another percentage of different base.

However, if you use the method of equal numerator method as mentioned by MathIzzzFun and StaryNight, you can use model method to show your child the whole concept of why we make the numerator the same.

Hope it helps!