Q&A - PSLE Math

[JadeDry]

CoffeeCat:

JadeDry:

Good Day.


I would appreciate it if someone could check whether my working is correct on the following Question:

A Polygon has N-sides. One of It's Interior angles is 126 degrees, while the other angles are each equal to 162 degrees, find the value of N.

My working:

Sum of Exterior Angles of a Polygon= 360 degrees.

Therefore: Largest Exterior angle = 180-126= 54 degrees.

Smallest Exterior angle= 180-162=18 degrees.

360-54= 306

306/18= 17 =(N-1) sides

therefore the Polygon has 18 sides.

Is this correct?

Thanks in advance.

Yes, you are absolutely correct!

Thank you!

[mvmir26]

Anyone can help me with below questions:-

Mr Tan had a total of 350 ducks and chickens in his farm. After selling some ducks and chickens he had 100 of them left. The ratio of the number of chickens sold to the number of chickens left was 4:1. The number of ducks sold to the number of ducks left was 3:2. How many chickens were sold by Mr Tan?

[tianzhu]

mvmir26:

Anyone can help me with below questions:-

Mr Tan had a total of 350 ducks and chickens in his farm. After selling some ducks and chickens he had 100 of them left. The ratio of the number of chickens sold to the number of chickens left was 4:1. The number of ducks sold to the number of ducks left was 3:2. How many chickens were sold by Mr Tan?

Hi

This is a question on simultaneous concepts.

If a student is familiar with simultaneous equations, he/she may use it.

If not,solve it using the ‘Alphabet Method” or solve the equations pictorially.

Let’s begin using the “Alphabet Method”

Number of chickens sold ------ 4C
Number of chickens left ------ 1C

Number of ducks sold ------ 3D
Number of ducks left ------2D

5C + 5D ------350
1C + 1D ------70

1C + 2D ------ 100
1D -------30
1C ------40

Number of chicken sold --------4*40 ------160

Best wishes

[ozora]

I couldn’t get the answers. Pls help.

1.K and E had $362. When K gave 1/5 of his money to E, E had $46 more than K. How much did K and E have at first respectively?
2.Joan bought some apples and put them into boxes.
if she put 4 apples into each box, there would be 3 apples left.
if she put 6 apples into each box, there would be 5 apples left.
if the number of apples was between 100 to 150, how many apples did Joan buy?.

[tianzhu]

Hi


For Q1, a student should recognize that the amount of money stays the same after the transfer.

As for Q2, “Systematic Listing” is commonly used by students.
There are multiple answers to your question.
107 is one of them. I think there are three more answers, 119, 131 and 143.

Hope this helps.

Best wishes.

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[zsqchx]

Hi, Someone can help for the following question. Thanks!


There are some red and blue pencils in a box. If 30 red pencils are taken out from the box. the total number of pencils left will be 8 times the number of red pencils left. If 50 blue pencils are taken out from the box. the total number of pencils left will be thrice that of the number of blue pencils left. How many pencils are there in the box?

[jesschan]

This is a P5 maths question - not sure is this the correct place to post.


A man spent $1119 on a diamond using $50, $5 and $2 notes. The total number of notes used is 45. How many $50, $5 and $2 notes did he use?

I know how to solve it using Guess and Check - just wondering if there is a quicker method?

[tianzhu]

Hi zsqchx


This is a two scenarios question on \"double if \". It's quite an interesting one.

Hope this helps.

Best wishes

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[jieheng]

zsqchx:

Hi, Someone can help for the following question. Thanks!


There are some red and blue pencils in a box. If 30 red pencils are taken out from the box. the total number of pencils left will be 8 times the number of red pencils left. If 50 blue pencils are taken out from the box. the total number of pencils left will be thrice that of the number of blue pencils left. How many pencils are there in the box?

Model 1
R [ ][30]

B [ ][ ][ ][ ][ ][ ][ ]

When 50 blue pencils are taken out , ration of red pencils to the blue pencils is 2 : 1

Modified the model 1 , [ ] = [ ][ ]
Model 1
R [ ][15][ ][15]

B [ ][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ] (14u)

Model 2
R [ ][15][ ][15] (2u+30)

B [ ][15][----------------50---------------] (1u+15+50)

Compare the Blue pencils of the models 1 and 2

14u = 1u + 15 + 50

13u = 65

1u = 5

From the model 1 ,

Total number of the pencils in the box = 16u + 30 = 16 * 5 + 30 = 110 (Ans)

[zsqchx]

Thank you! Tianzhu and Jie Heng