Q&A - PSLE Math

[lizawa]

tianzhu:

Maths Questions from http://www.channelnewsasia.com/discussion/forum.htm


3. A group of people met at a party. Each person shook hands with everyone else. Mr Li shook hands with 3 times as many men as women. Mrs Li shook hands with 4 times as many men as women. How many men and how many women were there at the party?

Answer : no. of men = 16; no. of women = 5

See working :

http://www.postimage.org/image.php?v=gx2w0utS

[suiyuan]

Q47

Please help to establish the number pattern for Q47 in this link.
http://www.wendykoh.com/08/primary6-aitongca1-maths.pdf

[lizawa]

suiyuan:

Q47

Please help to establish the number pattern for Q47 in this link.
http://www.wendykoh.com/08/primary6-aitongca1-maths.pdf

Stage Squares
1 ===> 1
2 ===> square (2+1) - (1*4) = 5
3 ===> square (3+2) - ((2+1) *4) = 13
4 ===> square (4+3) - ((3+2+1)*4) = 25
5 ====> square (5+4) - ((4+3+2+1)*4) = 41
10 ===> square (10+9) - ((9+8+7+6+5+4+3+2+1) *4) = 181
100 ==> square (100+99) - ((99+98+97+...+1)*4) = 19801

nth stage == > square (n+(n-1)) - ((sum of (n-1, n-2, n-3....1)*4)

So you take the area of the whole figure at each stage- (no of squares cut of each edge * 4 edges).

to solve 99+98+...1 at primary level, no need to teach AP/GP,
just re-arrange 1+2+.. 99 and place them under 99+98... +1
So you get 1 term as (99+1), (98+2) etc. ie. each term is 100. Total 99 terms. So sum = (100*99) / 2

[ApronMama]

suiyuan:

Q47

Please help to establish the number pattern for Q47 in this link.
http://www.wendykoh.com/08/primary6-aitongca1-maths.pdf

How about this series ? Answer same as Lizawa's

Stage Squares
1 ===> 1
2 ===> 1+4(2-1) = 5
3 ===> 1+4(2-1)+4(3-1) = 13
4 ===> 1+4(2-1)+4(3-1)+4(4-1)=25
5 ===> 1+4(2-1)+4(3-1)+4(4-1)+4(5-1)=41
.
.
10 ===>1+4(2-1)+4(3-1)+4(4-1)+4(5-1)+...+4(9-1)=181
.
.
nth ===>1+4(2-1)+....+4(n-1)

if n=100, we get
100 ===>1+4(2-1)+....+4(100-1)
=1+4*1+4*2+...+4*99
=1+4(1+2+....+99)
=1+4(4950)
=19801
{ to do 1+2+3+...+99 same as Lizawa's method to pair up (1+99), (2+98),... you get 49*pairs of 100 +50 = 4950}

[lizawa]

Hi Apronmama,


Maybe yours is an easier method. I assume calculator can be used. But just realized that last year’s P6 still no calculator allowed.

[tianzhu]

Thank You for your help.


What is the number pattern for Q46 of this link?
http://www.wendykoh.com/08/primary6-aitongsa1-maths.pdf

[sms]

tianzhu:

Thank You for your help.


What is the number pattern for Q46 of this link?
http://www.wendykoh.com/08/primary6-aitongsa1-maths.pdf

Is the answer 35?.

[tianzhu]

Another look at Q3


http://farm4.static.flickr.com/3268/3211341130_6bb582e540_o.jpg\">

[tianzhu]

AnnT2009:

Hi csc,


Sorry! Still confused, don't they meet somewhere in the middle of the journey.

Thanks for your patience.

Hi, hope this helps.

http://farm4.static.flickr.com/3379/3222658500_6fe616c3ee_o.jpg\">

[small]

lizawa:

tianzhu:

Maths Questions from http://www.channelnewsasia.com/discussion/forum.htm


3. A group of people met at a party. Each person shook hands with everyone else. Mr Li shook hands with 3 times as many men as women. Mrs Li shook hands with 4 times as many men as women. How many men and how many women were there at the party?

Answer : no. of men = 16; no. of women = 5

See working :

http://www.postimage.org/image.php?v=gx2w0utS

Hi lizawa,

I was not able to see the picture clearly, please can you send it to me or repost? thanks in advance.

Anyway I have to say thanks to all, great forum...help me a lots.