Q&A - PSLE Math

[tianzhu]

zanen:

Hi I'm Zan En's sister and would like to ask this qns on her behalf. Mrs Leong had white and orange ping pong balls in the ratio 7:5. She then replaced several white ping pong balls with orange ones keeping the total number of ping pong balls the same. The ratio of the number of white ping pong balls to orange ping pong balls became 3:5.

(a) If the total number of ping pong balls is not more than 30, how many white ping pong balls did Mrs Leong have at first? (b) How many new orange ping pong balls were used to replace the white ones?

Hi

White:Orange ------ 7:5(12)------- 14:10 (24)

White:Orange ------ 3:5(8) ------- 9:15(24)

Number of white balls@first ------- 14

Number of orangeballs@replacing white balls ------- 15-10 ------ 5

Best wishes

[tianzhu]

Shimmer:

One more question pls!


Dean,Ellen and Andy shared a box of sweets in the ratio of 3:4:5 and there was 4 left .They put the 4 sweets into a second box which contained 1/8 fewer sweets than the first box, and shared the sweets in the same ratio as before,and this time there were no remainder.
A)Find the total number of sweets they shared in the first round.
B)Find the total number of sweets each child received in both rounds of sharing.

Hi

Where is this question from?

What are the answers in the WS?

I think there is a possibility of multiple answers.

One set of possible answers

a) 60 sweets

b) 30,40,50

Best wishes

[tianzhu]

Winx5015:

1)There were a total of 800 paper clips in 3 containers, A, B and C.Alex transferred 3/8 of the paper clips from container A to container B.He then transferred 40 paper clips from container B to container C.As a result, the number of paper clips in container C is 1/5 the number of paper clips in container A There were 264 paper clips in container B at first. How many paper clips were there in container A at first?

Hi

It’s useful to draw a simple diagram to show the flow.

After the transfer

A ------- 5 units

B ------- 224 + 3 units (40 transferred to C, hence 264-40 ----- 224, and 3 units received from A)

C ------- 1 unit (1/5 the number of paper clips in container A)

9 units + 224 ------- 800

1unit ------- 64

A ------- 8*64 -------- 512

Best wishes

[Shimmer]

tianzhu:

Shimmer:

One more question pls!


Dean,Ellen and Andy shared a box of sweets in the ratio of 3:4:5 and there was 4 left .They put the 4 sweets into a second box which contained 1/8 fewer sweets than the first box, and shared the sweets in the same ratio as before,and this time there were no remainder.
A)Find the total number of sweets they shared in the first round.
B)Find the total number of sweets each child received in both rounds of sharing.

Hi

Where is this question from?

What are the answers in the WS?

I think there is a possibility of multiple answers.

One set of possible answers

a) 60 sweets

b) 120 sweets

Best wishes[/quote

This question was given by my TUTION teacher.
Y

[anneshirleygilbert]

Hi MathIzzzFun,


I really appreciate you staying up so late to help me with the question on the big and small beads. Thank you so much.

Anne

[MathIzzzFun]

Shimmer:

One more question pls!


Dean,Ellen and Andy shared a box of sweets in the ratio of 3:4:5 and there was 4 left .They put the 4 sweets into a second box which contained 1/8 fewer sweets than the first box, and shared the sweets in the same ratio as before,and this time there were no remainder.
A)Find the total number of sweets they shared in the first round.
B)Find the total number of sweets each child received in both rounds of sharing.

This looks more like a MO question than a PSLE question.

3+4+5 =12
Number of sweets in 1st box, after removing 4 sweets = 12 units
Number of sweets in 2nd box, after adding 4 sweets = 12 parts
Number of sweets in 1st box : 2nd box
= 12 units + 4 : 12 parts - 4
= 8 :7

equalize: 84 units + 28 = 96 parts - 32
7 units + 5 = 8 parts
8 units - 8 parts = 1 unit - 5

smallest possible value of 1 unit --> 1 unit - 5 = 0
1 unit --> 5 (subsequent values : 13, 21, 29 ....)
1 part --> 5

a) Total number of sweets shared in first round (smallest number)
= 12 units = 12 x 5 = 60
b) Total number of sweets shared in both rounds = 12 units + 12 parts = 120
Dean --> 3/12 X 120 = 30 sweets
Ellen --> 4/12 x 120 = 40 sweets
Andy --> 5/12 x 120 = 50 sweets

Other possible answers:

http://i48.tinypic.com/2zrqlb8.png\">

cheers.

[student101]

I tried different way to solve below problem for last couple of days. Pls help me as I feel very difficult to get the solution:


At a fitness carnival, 1600 people participated in a Mass dance & Taji. 30% of 1300 Mass dance participants were adults and 40% of Taji participants were children. During the break, some Mass dance participants went on to particiapte in Taji, while some Taji participants went on to particiapte in Mass dance. After the change, 25% of the mass dance participants and 75% of the Taji particiapants were adults. How many Mass dance participants were there after the change?

[AceTutors123]

--- :scratchhead: ---

[AceTutors123]

Got this by a bit of trial and error (just 1 hehe).


http://www.acetutors.com.sg/images/MassdanceTaji2.png\">

Thus there were 1460 people doing the mass dance thereafter. Taji is too slow for the crowd at the event =D

[maychang]

I’m trying to upload a image. As the instruction for upload a file and click the Add To Post button to add it to your post, however i couldn’t find the "Add to Post" button in the screen.


Anyone has the same issue?