Q&A - PSLE Math

[tianzhu]

Hi elkniwt


This question touches on simultaneous concept.

You may solve it pictorially, using letters of the alphabet or units and parts. There are some examples in some of the earlier posts.

For this question, I’ve chosen 125%:100% as 25:20 so as to make the calculations neater.(5P ----- 20, so you'll get a whole number for P instead of decimals.)

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7161/6707675849_d6e9dec552_z.jpg\">

[sleepyqueen]

PiggyLalala:

MathIzzzFun:

Hi

http://www.flickr.com/photos/62167097@N02/6705370185/in/photostream

cheers.

Hi MathizzFun,
Can explain how do we know we have to let C to be 75 units?
Thank you very much

Should be \"How to get C to be 60 units\" as presented in the solution
A+B = 125% if C = 75 units. But there is no C = 60 units mentioned in the question.

[MathIzzzFun]

elkniwt:

Hi MathIzzzFun,

Wow! Thank you for the model method. It's ingenious!! hmm... wonder if my dd can digest it or not. I'll try to explain to her.

Hi sleepyqueen,
My method is similar to yours. I am a bit hesitant to teach my dd simultaneous equations. Are they allowed to use this method?

Thanks everyone!

Hi

u r welcome

cheers.

[MathIzzzFun]

PiggyLalala:

MathIzzzFun:

[quote=\"elkniwt\"]
Here's the question. I put in 125% in red (only my guess).
http://i44.tinypic.com/1zr1jq9.jpg\">

Dear tianzhu and MathIzzzFun,
I only know how to do this question using simultaneous equations. :oops: Could you please help to advise how to do this question in suitable method. Thank you very much.

Hi

http://www.flickr.com/photos/62167097@N02/6705370185/in/photostream

cheers.

Hi MathizzFun,
Can explain how do we know we have to let C to be 75 units?
Thank you very much[/quote]Hi

given Area A + Area B = 125% of Area C
so Area A + Area B : Area C = 5 : 4

We can use 5 units for area A + area B and 4 units for area C but we will need to deal with fractions/decimals. Since 1/5 of C was shaded, I decided on a multiple of 20 which is 60 units, but if one is comfortable dealing with decimals, then you can just set area C = 20 units.

cheers.

[pixiedust]

Bunny27:

1.Steven read an equal number of pages from a storybook each day. After 12 days, he had 4/5 of the pages left. After another 10 days, he had 570 pages left. How many pages were there in the storybook?

2. Samuel is 1/4 as old as Meihui. In 5 year's time, Samuel will be 1/3 as old as Meihui. How old is Meihui now?

TIA

Q1>

12days reads 1/5 pages
1 day reads 1/5 divide 12 = 1/60 pages
22 days reads 1/60*22=11/30 pages
Hence 19U->570, U=30
Total pages = 30*30=900

Q2>

Now - S : 1U, MH : 4U -> age difference : 3U
5yrs later - S : 1P, MH : 3P -> age difference : 2P

2P = 3U
1P=1U+5
2(1U+5)=3U
1U=10

Mei Hui is 40 years old now.

[elkniwt]

Dear tianzhu,


Your illustration is always so clear and so beautiful. Thank you very much.

[Bunny27]

Hi, sorry I need someone to help me with one more question..


Kellie took 4 tests. The average mark for the 4 tests was q. She obtained 60 marks for the first test and 75 marks for the second test. Given that she obtained q marks in the third test, find how many marks Kellie obtained in the fourth test.

TIA

[Suz855]

Total marks for 4 tests = 4q


Marks for the 4th test --> 4 q- 60-75-q =3q-135

[jesschan]

Deleted.

[Bunny27]

Suz855:

Total marks for 4 tests = 4q


Marks for the 4th test --> 4 q- 60-75-q =3q-135

Thank u