Q&A - PSLE Math

[spunky]

Thanx so much for ur help.

tianzhu:

spunky:

SCGS SA2 2009
Ahmad and Halim together took 5 days to paint their house. If Ahmad and Halim work together for 2 days, followed by Ahmad working alone for 8 days, Halim will take 1 more day to complete the remaining work. How long will Ahmad take to apint the house all by himself?

Hi

This question touches on “Rates”.

There is more than one way to solve it.

One possible solution is:

When Ahamd and Halim work together, they can paint their house in 5 days.
In 1 day, they can paint 1/5 of their house or 1 unit.

Hence, 1 day of Ahmad + 1 day of Halim ----- 1 unit

In 2 days, they can paint 2/5(2 units) of their house, this means 3/5(3 units) of their house is left unpainted.

8 days of Ahmad + 1 day of Halim ----- 3 units
1 day of Ahmad + 1 day of Halim ----- 1 unit

Therefore, 7 days of Ahmad ----- 2 units
17.5 days ----- 5 units(whole house)

Ahmad took 17.5 days to paint the house all by himself.

Best wishes

[MathIzzzFun]

christina soh:

MathIzzzFun:

[quote=\"christina soh\"]

Hi MathIzzzFun,

What is your answer for Q14 of Paper 1 (math) of the following school?

http://www.orlesson.org/orp/09Ma/2009-P6-Math-SA2-PLMGS.pdf

Hi

77 blocks... the blocks need not be oriented in the same way..

cheers.

Thank you very much MathIzzzFun. Would you mind let me have the working?[/quote]Hi

http://i54.tinypic.com/27y8gh0.jpg\">

cheers.

[MathIzzzFun]

TT2:

Hi MathIzzzfun,


Thanks for your help. Noticed that e cross-multiply way is sometimes used to solve e ratio problems n sometimes e model method can be used. My son is not familiar on e 1st method. When do we use e cross multiply method or die die must use this? Eg. There is movement of e items???? :? Pls help...... :imdrowning:

Thanks a lot

Hi

I have added \"visuals\" to make the cross-multiply method easier to understand...

http://i56.tinypic.com/i3tr1w.jpg\">

here's the solution using models...

http://i53.tinypic.com/13z075u.jpg\">

cheers.

[TT2]

:thankyou:

MathIzzzFun:

TT2:

Hi MathIzzzfun,


Thanks for your help. Noticed that e cross-multiply way is sometimes used to solve e ratio problems n sometimes e model method can be used. My son is not familiar on e 1st method. When do we use e cross multiply method or die die must use this? Eg. There is movement of e items???? :? Pls help...... :imdrowning:

Thanks a lot

Hi

I will post the model solution later.. in a rush now.. and also the cross multiply method.

cheers.

[MathIzzzFun]

TT2:

:thankyou:

MathIzzzFun:

[quote=\"TT2\"]Hi MathIzzzfun,


Thanks for your help. Noticed that e cross-multiply way is sometimes used to solve e ratio problems n sometimes e model method can be used. My son is not familiar on e 1st method. When do we use e cross multiply method or die die must use this? Eg. There is movement of e items???? :? Pls help...... :imdrowning:

Thanks a lot

Hi

I will post the model solution later.. in a rush now.. and also the cross multiply method.

cheers.

[/quote]u r welcome

cheers.

[MathIzzzFun]

stary:

Thanks MathIzzzFun for your prompt reply!

u r welcome

cheers.

[stary]

MathIzzzFun:

stary:

Thanks MathIzzzFun for your prompt reply!

u r welcome

cheers.

[Verysuperkiasu]

Have a question on math - if the questions do not require the child to reduce answer to lowest form (for fractions), MUST they do it? Will marks be deducted if they don't? My son's teacher advises them not to reduce to lowest if not specified in the question for fear that the chn may make careless mistakes in the process of reducing to lowest term. However, I seem to recall my time in school, the teacher emphasised MUST reduce fractions to lowest form even if not asked to do so. Has the requirements change since then?

[ozora]

Hi need some help in these 2 questions.


Mac bought some apples and gave half to Jack.
Jack bought some oranges and gave half to Mac.
Mac threw away 25 rotten oranges and Jack bought another 25 apples for himself.
In the end, the number of oranges to the number of apples Mac had was 1:4 and the number of oranges to the number of apples Jack had was 1: 2.
How many oranges did Jack buy?

2.Mr Lee had some buttons for sale. 3/5 of them were black and the rest were white. After selling 120 white buttons and 5/9 of the black buttons, he had 2/5 of the buttons left. How many buttons did he sell in all?

[iFirefly]

Verysuperkiasu:

Have a question on math - if the questions do not require the child to reduce answer to lowest form (for fractions), MUST they do it? Will marks be deducted if they don't? My son's teacher advises them not to reduce to lowest if not specified in the question for fear that the chn may make careless mistakes in the process of reducing to lowest term. However, I seem to recall my time in school, the teacher emphasised MUST reduce fractions to lowest form even if not asked to do so. Has the requirements change since then?

DS says teacher told them must reduce fractions to lowest form, even if question does not specify. DS is from GEP but his friends from mainstream are taught that way too.