Q&A - PSLE Math

[sokk]

Maths Hub:

sokk:

I need help for this question.


Rita and Molly shared some stickers between them.
If Rita gives 15 of her stickers to Molly, Molly will have thrice as many stickers as Molly.
If Molly gives 15 of her stickers to Rita, Rita will have twice as many stickers as Molly.
How many stickers does each of them have?


Thanks!!

Hi, I presume you mean

Rita and Molly shared some stickers between them.
If Rita gives 15 of her stickers to Molly, Molly will have thrice as many stickers as Rita.
If Molly gives 15 of her stickers to Rita, Rita will have twice as many stickers as Molly.
How many stickers does each of them have?

1) If Rita gives 15 of her stickers to Molly, Molly will have thrice as many stickers as Rita.

Molly: 3 units
Rita: 1 unit

2) Start (If Rita didn't gives 15 of her stickers to Molly)

Molly: 3 units -15
Rita: 1 unit + 15

3) If Molly gives 15 of her stickers to Rita

Molly: 3 units - 30
Rita: 1 unit + 30

Now, Rita has twice of Molly, meaning
(3 units - 30) X 2 --> 1 unit + 30
6 units - 60 --> 1 unit + 30
5 units --> 90
1 unit--> 18

Therefore Molly at start: 3 units - 15 --> 3 X 18 - 15 = 54 - 15 = 39
Rita at start: 1 unit + 15 --> 18 + 15 = 33

Hope that helps.

Hi,
Thanks for the quick reply. But when I try to work out the story using Rita 33 and Molly 39 at first, I can't seems to get Rita having twice as many as Molly .

At first
Rita 33 Molly 39

after Rita gives Molly 15
Rita 18 , Molly 54
(Molly has thrice as many as Rita)

after Molly gives Rita 15
Rita 33 , Molly 39
(I can't arrive at Molly having twice..)

Did I interpret the question wrongly??
Please help! getting confuse....

[Maths Hub]

sokk:

Hi,
Thanks for the quick reply. But when I try to work out the story using Rita 33 and Molly 39 at first, I can't seems to get Rita having twice as many as Molly .

At first
Rita 33 Molly 39

after Rita gives Molly 15
Rita 18 , Molly 54
(Molly has thrice as many as Rita)

after Molly gives Rita 15
Rita 33 , Molly 39
(I can't arrive at Molly having twice..)

Did I interpret the question wrongly??
Please help! getting confuse....

Hi,

After Molly give Rita 15
Rita 48, Molly 24
(Rita is twice Molly, not the other way round)

Hope that helps.

[sokk]

.

[tianzhu]

Hi moderators


Please help to delete.

Best wishes

[sokk]

tianzhu:

sokk:

I need help for this question.


Rita and Molly shared some stickers between them.
If Rita gives 15 of her stickers to Molly, Molly will have thrice as many stickers as Molly.
If Molly gives 15 of her stickers to Rita, Rita will have twice as many stickers as Molly.How many stickers does each of them have?



Thanks!!

Hi

Perhaps, it should be read as “If Molly gives 15 of her stickers to Rita, Molly will have twice as many stickers as Rita.

Best wishes

Hi,
Yes, hehe, it was my typo error. Whole morning been confused by this Molly Rita question. hahaha...
I have interpreted wrongly, thinking that after Rita gives Molly 15 stickers , Molly proceeds to give Rita 15 stickers. Hence I arrived at the answer
Molly 12 stickers and Rita 24 stickers.


Hi MathsHub
Thanks for the help!

[sokk]

Maths Hub:

sokk:

Hi,
Thanks for the quick reply. But when I try to work out the story using Rita 33 and Molly 39 at first, I can't seems to get Rita having twice as many as Molly .

At first
Rita 33 Molly 39

after Rita gives Molly 15
Rita 18 , Molly 54
(Molly has thrice as many as Rita)

after Molly gives Rita 15
Rita 33 , Molly 39
(I can't arrive at Molly having twice..)

Did I interpret the question wrongly??
Please help! getting confuse....

Hi,

After Molly give Rita 15
Rita 48, Molly 24
(Rita is twice Molly, not the other way round)

Hope that helps.

Hi Maths Hub,
Thank you very much for your help! I understand now.

[RelaxedMum]

iCreative Math:

Yum Yum, your question below:-


1) Mary bought some red marbles and have half to Noel.
Noel bought some blue marbles and gave half to Mary.
Mary lost 16 red marbles and Noel lost 55 blue marbles.
The ratio of Mary's red marbles to blue marbles became 18:85 and the ratio of Noel's red marbles to blue marbles became 7:20.
How many red marbles did Mary buy?

is adapted from the 2009 PSLE question with changes to the numbers and the resultant ratios but they are essentially similar questions.

I have posted the explanation of the solution to the 2009 PSLE question in YouTube (see the link below).

I hope the verbal explanation will be helpful for your child to understand the solution to this sort of questions.

http://www.youtube.com/watch?v=epaXFwd5j_0

Best Regards,

iCreative Math

Many thanks for the explanation

[superksmum]

Hi, can someone please help:


Mrs Tan had 130 apples and oranges. After she sold 2/3 of the apples and 2/5 of the oranges, she had 36 more apples than oranges left. How many fruits had she left in all?

[superksmum]

Hi, another question:

Aaron, Betsy, Charmaine and Deon share the cost of a friend’s birthday present equally. As Aaron only had $2 with him, the rest of his share was paid by his friends first. The ratio of the total amount of money Betsy and Charmaine paid to that Deon paid is 7:5. If Aaron returned $15 to Deon, find the cost of the present.

Thanks

[MathIzzzFun]

superksmum:

Hi, another question:

Aaron, Betsy, Charmaine and Deon share the cost of a friend's birthday present equally. As Aaron only had $2 with him, the rest of his share was paid by his friends first. The ratio of the total amount of money Betsy and Charmaine paid to that Deon paid is 7:5. If Aaron returned $15 to Deon, find the cost of the present.

Thanks

amount paid by Betsy & Charmaine : Deon --> 7u : 5u -- total 12u

total cost of present --> 12u + $2
each person --> 3u + $0.50

Aaron's share paid by Deon --> 5u - 3u - $0.50 2u - $0.50

2u - $0.50 = $15
1u --> $7.75

Cost of present --> 12 x $7.75 + $2 = $ 95

cheers.