Q&A - PSLE Math

Academic support for Primary 6 and PSLE
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EconsPhDTutor
OrangeBelt
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Re: Q&A - PSLE Math

Post by EconsPhDTutor » Thu Mar 10, 2016 10:26 am

taringal wrote:Hi,

Can someone help on the following questions with clear explanation? Thank you.

Q1) May, Susan, Ben and Joey, each have some stickers. May has 50% as many stickers as the total number of stickers that Susan, Ben and Joey have. The number of stickers that Susan has is 25% of the total number of stickers that May, Ben and Joey has. The number of stickers that Ben has is 2/3 of the total number of stickers that May, Susan and Joey has. If May gives 20 stickers to Susan, May and Susan will then have an equal number of stickers. Find the average number of stickers each of them has.

Q2) In a donation drive, Ali, Hendri, Danny and Kaviin collected an average of $128. Ali collection 1/7 of the total amount collected by Hendri, Danny and Kaviin. Hendri collected 2/5 of the total amount collected by Danny and Kaviin. Danny collected 1/3 as much donations as Kaviin. How much donations did Ali collect?

Q3) A wallet contained some 2-dollar and 5-dollar notes in the ratio of 8:3. When 15 2-dollar notes were taken out and replaced with some 5-dollar notes, there was 16% less 5-dollar notes than 2-dollar notes. The total value of all the notes remained the same. What is the total value of all the notes in the wallet?
Hi Taringal, the answers are

(1) 75.
(2) $64.
(3) $155.

Please see this PDF for the full solutions.

Best
Dr. Choo Yan Min

www.EconsPhDTutor.com

whywhy
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Re: Q&A - PSLE Math

Post by whywhy » Tue Mar 15, 2016 6:41 pm

Please help with this question. Thank you.
When Mr Lee was 40 years old, his son was twice his daughter's age. Mr Lee would be twice his son's age when his daughter was 28 years old. How old would Mr Lee be when his daughter was 20 years old?

EconsPhDTutor
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Re: Q&A - PSLE Math

Post by EconsPhDTutor » Tue Mar 15, 2016 7:35 pm

whywhy wrote:Please help with this question. Thank you.
When Mr Lee was 40 years old, his son was twice his daughter's age. Mr Lee would be twice his son's age when his daughter was 28 years old. How old would Mr Lee be when his daughter was 20 years old?
Let x be how much older the son is than the daughter.

Let L be Mr Lee's age when his daughter was 20 years old. (Keep in mind that L is the answer we are looking for.)

And so when his daughter was 28 years old, Mr Lee was (L + 8) years old and his son was (28 + x) years old. From the second sentence:

L + 8 = 2 × (28 + x) ⇒ L + 8 = 56 + 2x ⇒ L - 48 = 2x ⇒ ½L - 24 = x.

Let's save the above for later.

From the first sentence, when Mr Lee was 40 years old, his son was 2x years old and his daughter was x years old.

Hence, Mr Lee is (40 - x) years older than his daughter. And so when his daughter was 20 years old, Mr Lee was L = 60 - x years old. Substitute what we had from above:

L = 60 - x = 60 - (½L - 24) = 84 - ½L ⇒ 1.5L = 84 ⇒ L = 56.

The answer is L = 56. ∎

Hope this helps and feel free to ask for any clarifications.

- Dr. Choo Yan Min

sushi88
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Re: Q&A - PSLE Math

Post by sushi88 » Tue Mar 15, 2016 7:47 pm

whywhy wrote:Please help with this question. Thank you.
When Mr Lee was 40 years old, his son was twice his daughter's age. Mr Lee would be twice his son's age when his daughter was 28 years old. How old would Mr Lee be when his daughter was 20 years old?
Image

whywhy
OrangeBelt
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Re: Q&A - PSLE Math

Post by whywhy » Wed Mar 16, 2016 7:49 pm

Thank you all for helping esp Sushi 88 for the model solution.


StillThinking
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Re: Q&A - PSLE Math

Post by StillThinking » Wed Mar 16, 2016 8:25 pm

taringal wrote:Hi,

Can someone help on the following questions with clear explanation? Thank you.

Q1) May, Susan, Ben and Joey, each have some stickers. May has 50% as many stickers as the total number of stickers that Susan, Ben and Joey have. The number of stickers that Susan has is 25% of the total number of stickers that May, Ben and Joey has. The number of stickers that Ben has is 2/3 of the total number of stickers that May, Susan and Joey has. If May gives 20 stickers to Susan, May and Susan will then have an equal number of stickers. Find the average number of stickers each of them has.

Q2) In a donation drive, Ali, Hendri, Danny and Kaviin collected an average of $128. Ali collection 1/7 of the total amount collected by Hendri, Danny and Kaviin. Hendri collected 2/5 of the total amount collected by Danny and Kaviin. Danny collected 1/3 as much donations as Kaviin. How much donations did Ali collect?

Q3) A wallet contained some 2-dollar and 5-dollar notes in the ratio of 8:3. When 15 2-dollar notes were taken out and replaced with some 5-dollar notes, there was 16% less 5-dollar notes than 2-dollar notes. The total value of all the notes remained the same. What is the total value of all the notes in the wallet?
For Q3, when it said replaced, did it mean 15 notes, or the worth of 15 $2 notes? or just a random number of $5?
I assumed that it meant 15 notes...
2x8u=16u
5x3u=15u
2x15=30
5x15=75
8u-15=100x
3u+15=84x
31u=?
8400x=672u-1260=300u+1500
372u=1500+1260=2760
then it is no longer divisible, cld someone take a look and help(I'm known for being Ms Careless)

taringal
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Re: Q&A - PSLE Math

Post by taringal » Sun Mar 20, 2016 3:57 pm

Hi,

Can someone help on the following questions? Thank you.

Question 1

A factory made 135 more blueberry muffins than egg tarts. After 3/5 of the blueberry muffins and 1/4 of the egg tarts were taken away, there were 198 more egg tarts left than blueberry muffins.

(a) How many egg tarts were made at the factory at first?
(b) How many blueberry muffins were taken away?

Question 2

Mdm Kee collected 3 types of flowers from a nursery. 1/5 of them were roses, 2/5 of the remainder were carnations and the rest were daisies. There were 154 more daisies than roses.

(a) How many carnations were there?
(b) If Mdm Kee decided to sell each stalk of flowers for $5, how much money would she collect from the sale of all the flowers?

Question 3

Miss Fiona bought an equal number of markers and brushes for the Art club. She spent $275 altogether and each brush cost $1.50 more than a marker. If the ratio of the amount of money she spent on the markers to the amount of money she spent on the brushes was 7:4, how many brushes did she buy?

Question 4

A baker packed some fruit tarts into 6 small trays and 14 big trays. Each big tray can hold 12 more fruit tarts than each small tray. 13/16 of the fruit tarts were packed in big trays.

(a) What fraction of the tarts was packed in small trays? (Ans: 3/16)
(b) How many fruit tarts were there in a big tray? (please help on this)

questionable_i
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Re: Q&A - PSLE Math

Post by questionable_i » Sun Mar 20, 2016 6:13 pm

Can anyone help me with these questions?

1. Mrs Lim will make a profit which is 19% of the import price if she sells the necklace at $4165. What will be her profit if she sells the necklace at $4270 and the import price of the necklace remains constant?

2. Students are donating money to a charity fund that helps less privileged kids. The number of $2, $5 and $10-notes donated are in the ratio of 9 : 2 : 5.
4/9 of the $2-notes and 10 $5-notes are taken out. The remaining notes are worth $300. How many $10-notes are there?

:thankyou:

Ice watch
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Re: Q&A - PSLE Math

Post by Ice watch » Sun Mar 20, 2016 7:35 pm

questionable_i wrote:Can anyone help me with these questions?

1. Mrs Lim will make a profit which is 19% of the import price if she sells the necklace at $4165. What will be her profit if she sells the necklace at $4270 and the import price of the necklace remains constant?

2. Students are donating money to a charity fund that helps less privileged kids. The number of $2, $5 and $10-notes donated are in the ratio of 9 : 2 : 5.
4/9 of the $2-notes and 10 $5-notes are taken out. The remaining notes are worth $300. How many $10-notes are there?

:thankyou:
Image


Image

forestcadee
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Re: Q&A - PSLE Math

Post by forestcadee » Sun Mar 20, 2016 8:32 pm

Hi, can someone help to solve the following 2 questions on circles? Thank you.

Image


Image

:thankyou:

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