Q&A - PSLE Math

[tianzhu]

Hi


I think the question asks for the amount of water in Beaker A and B in the beginning.In this question, a student should note that the total amount of water stays at 9 litres before and after.

You may use \"working backwards\" to solve this question, either using MD or UM.As usual, I've shown more models than necessary to show the flow of events.

The answers are Beaker A ---- 2.7 litres and Beaker B ---- 6.3 litres.They add up to 9 litres.

Hope this helps.

Best wishes.

http://farm6.static.flickr.com/5107/5629194647_8b4e1c1753_z.jpg\">

[fxchow]

jieheng:

fxchow:

Hi,


Can anyone help on this question. TIA

There were 370 members in a club last year.
This year, the number of male member has reduced by 10% and the number of female member has reduced by 5%.
There are as many male members as female members now.
How many members are there in the club now?

fxchow

M [-------------9u-------------][-----1u-----] (total 10u)

F [------------9.5u------------][-0.5u-] (total 10u)


given there are as many male members as female members now ,

change the 9u and 9.5u to the common multiples 9*9.5 = 85.5u

M*9.5 and F*9

M [--------9u*9.5-----------][--1u*9.5---] (total 95u)

F [--------9.5u*9-----------][0.5u*9] (total 90u)


M [--------85.5u-----------][--9.5u---] (total 95u)

F [--------85.5u-----------][4.5u] (total 90u)

total number of members in a club last year = 95u + 90u = 185u

185u -----> 370

1u -----> 2

number of members are there in a club now = 85.5u * 2 = 171u = 171 * 2 = 342 (Ans)

Hi JieHeng,

Thanks for your solution.

fxchow

[teddy7171]

Plz HELP.


1) Farmer Tan has ducks and cows on his farm. the total number of ducks and cows is between 20 and 40. the ratio of the total number of ducks’ legs to the total number of cows’ legs is 5:9. What is the total number of ducks and cows on the farm?

2) Mdm Lek had 57 apples and oranges altogether. there were 3 fewer oranges than apples. she gave away half as many oranges as apples to her neighbours. she was left with twice as many oranges as apples. how many apples did she give away?

Thank U.

[tianzhu]

Hi


For Q2, students should have a smooth start with the first step.

57-3 = 54
54/2 = 27
Mdm Lek has 27 oranges and 30 apples at first.

The turbulence may start when students are expected to solve two equations with two unknowns. For those who are familiar with SE, they may proceed with it.

In dealing with such questions, students may solve using letters of the alphabet or solve the equations pictorially which I’ve shown in this post.

Hope this helps.

Best wishes.

http://farm6.static.flickr.com/5146/5633327725_cf9a1e727a_z.jpg\">

[tianzhu]

Hi


A quick one for Q1

One needs to differentiate the ratios representing the number of legs and the number of animals. The ratios for the number of legs and the number of animals are of different measures.

The total number of ducks’ legs to the total number of cows’ legs is 5:9 ------ 20:36 (equivalent ratios)

A duck ----- 2 legs, a cow ----- 4 legs

This means the total number of ducks to the total number of cows ----- 10:9 -----20:18

Ducks ----- 20
Cows ----- 18

There are 38 ducks and cows.

Best wishes

[teddy7171]

Thank U ver much, Tianzhu.

[pixiedust]

Would appreciate any help on a systematic way to solve this :

[tianzhu]

Hi


I don’t think this is a PSLE maths question, more like a puzzle.

2178 x 4 = 8712

Best wishes

[tianzhu]

teddy7171:

Thank U ver much, Tianzhu.

Hi

You're welcome.

Best wishes

[pixiedust]

Hi Tianzhu, thanks. It is from worksheet given by ds’s school.

May I know the thinking process to derive the answer ?