Q&A - PSLE Math

[chl72]

Jcong:

Can u pls help me solve this maths problem?


The ratio of the mass of chicken to the mass of fish was 3:5. 16 kg of the fish was sold to customers. After that, the ratio of mass of chicken to the mass of fish was 7:9. Find the mass of fish at first.

Let me try.

At first,
C : F
3 : 5
(x7) (x7)
21 : 35

After 16kg fish sold,
C : F
7 : 9
(x3) (x3)
21 : 27

35U - 27U = 8U
8U -> 16kg
1U -> 2kg
35U -> 70kg

70kg of fish at first. Right?

[elkniwt]

Hi chl72,


Girls = 20%
Boys = 100%
So Boys are (100 - 20 80% more than the girls.

[jieheng]

chl72:

Need help in this, if the number of girls is 20% of the boys, how many percent more are the boys than girls? Thanks!

Girls 20%

Boys 100%

Percent of more boys than girls are = (100% - 20%) / 20% * 100% = 400 % (Ans)

When solving the percentage question ,

To compare the percentage of A to B (A more than B or A less than B) ,

The percentage =[ (A - B) / B ]* 100 %

[Jcong]

What I don’t understand why you X7 at first and X3 for the scond ratio? I apologise for not being very clever.

[jojo]

Jcong:

What I don't understand why you X7 at first and X3 for the scond ratio? I apologise for not being very clever.

May i know, this is for Primary X???

[tianzhu]

Hi


This question touches on “Before and After scenarios”. It’s important that a student note that the mass of chicken remains the same in both cases.

The mass of chicken remains unchanged, therefore we make the units representing the mass of chicken the same in the before and after scenarios. A commom multiple of 3 and 7 is 21.

Hope this helps.

Best wishes.

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[chl72]

jieheng:

chl72:

Need help in this, if the number of girls is 20% of the boys, how many percent more are the boys than girls? Thanks!

Girls 20%

Boys 100%

Percent of more boys than girls are = (100% - 20%) / 20% * 100% = 400 % (Ans)

When solving the percentage question ,

To compare the percentage of A to B (A more than B or A less than B) ,

The percentage =[ (A - B) / B ]* 100 %

Thank you jieheng!
English no good lah, so find it very difficult to understand the question when they phrase it like that.. :oops:

[jieheng]

chl72:

Thank you jieheng!
English no good lah, so find it very difficult to understand the question when they phrase it like that.. :oops:

Hi chl72 ,

You are welcome.

Regards,

[shurley197323]

Pls help. Anne had 9/10kg of sugar. She used 2/3 of the sugar to bake some cookies and the rest for a bowl of jelly.

(a) How many grams of sugar did she use for the jelly
(b) If she made 9 cookies of the same size, what fraction of a kilogram she use for each of them.
Thanks

[jieheng]

shurley197323:

Pls help. Anne had 9/10kg of sugar. She used 2/3 of the sugar to bake some cookies and the rest for a bowl of jelly.

(a) How many grams of sugar did she use for the jelly
(b) If she made 9 cookies of the same size, what fraction of a kilogram she use for each of them.
Thanks

[3/10kg][3/10kg][3/10kg]

[3/10kg][3/10kg] for making cookies

[3/10kg] for a bowl of jelly

a) number of grams that she used for the jelly = 3/10 kg = (3/10)*1000 = 300 g (Ans)

b)

9 cookies -----> 6/10

1 cookie -----> ( 6/10 ) /9 = 1/15

the fraction of a kilogram she use for each of the cookie = 1/15 (Ans)