Q&A - PSLE Math

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Andrew Lee:

Hi , guy
Can help me solve this two questions
Maha Bodhi,2011,prelim, Q3, Q4

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Hi,

For question 3:

As each child donated different number of pencils and the biggest number is 15, so we have to work from biggest number in order to get the smallest number.

1st child - 15
2nd child - 14
3rd child - 13
4th child - 12
5th child - 11
6th child - 10

Total number of pencils that donated by 6 children is 75, so we have 13 more pencils to go with 2 children

13 --- 9 + 4

The smallest number is 4.

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For question 4, flip the diagram for easier reference.


As the height of the both triangles is the same thus we can add up their base to calculate their total area.

Area of unshaded part ----- 1/2 x 40 x 18 - 75 = 285cm2

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For question 4:


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[Andrew Lee]

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For question 4:


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谢谢你们 :rahrah:

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Hi，


甭客气。。

[imacsg]

Hi MathIzzzFun,

Thanks for your solution. What method do you call this?

Below is my method but do not know where is my mistake.

--------------------------
Roy | L | 2u | 4 |
--------------------------
Joy | L | L | 1u |
---------------------

282-4 = 278
278 / 2 = 139

1L + 2u = 139 …x2
2L + 4u = 278
2L + 1u = 139
3u = 139

Then cannot solve the problem, do you know where is my mistake.

[MathIzzzFun]

imacsg:

Hi MathIzzzFun,

Thanks for your solution. What method do you call this?

Below is my method but do not know where is my mistake.

--------------------------
Roy | L | 2u | 4 |
--------------------------
Joy | L | L | 1u |
---------------------

282-4 = 278
278 / 2 = 139

1L + 2u = 139 ..........x2
2L + 4u = 278
2L + 1u = 139
3u = 139

Then cannot solve the problem, do you know where is my mistake.

Hi

Roy had $4 more --> $143
L+2u = 143

cheers.

[AJH]

AJH:

:scratchhead: :scratchhead: Hi - have trouble with these problems:


Q1. If Darren gives 12 of his seashells to Kim, he will have 4 times as many seashells as Kim. If Darren gives another 4 more seashells to Kim, he will have thrice as many seashells as Kim. How many seashells does Kim have? Ans: 4

Q2. A flask is 1/3 filled with chocolate powder. A teapot, twice as large as the flask, is 1/4 filled with chocolate powder. Then the flask and the teapot are each filled with water completely and all the contents are mixed together into a chocolate drink. What fraction of the chocolate drink is the chocolate powder?

I've got 7/12 but the ans is 5/18 :scratchhead:

Q3. There are 65 lamp posts along St. Andrew's Street. The lamp posts are arranged such that the distance between two lamp posts on the same side of the street is 20m. One lamp post is on the opposite side of the street at an equal distance between the two lamp posts. How long is St Andrew's Street? Ans: 640m

Thank you.

Hi - nd help with the above problems. Thank you.

[imacsg]

Hi MathIzzzFun,

Thanks. I notice my mistake.

[brastilava]

Hi, please help in this question:

Ans: (a) 138.06 cm2; (b) 83.91 cm

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