Q&A - PSLE Math

[nounou]

http://i50.tinypic.com/54yk9l.jpg\"> Some please help! :?: Need to double confirm answer to this Q.

Nanyang Prelim 2012 Q2.
:thankyou: :thankyou: :thankyou:

[nounou]

http://i46.tinypic.com/idhth5.jpg\">

:?: Please help! :imdrowning:
Nanyang Prelim 2012 Q18 :slapshead:
Answer given = 96
:thankyou: :thankyou: :thankyou:

[tianzhu]

Treelodge:

http://i46.tinypic.com/idhth5.jpg\">

:?: Please help! :imdrowning:
Nanyang Prelim 2012 Q18 :slapshead:
Answer given = 96
:thankyou: :thankyou: :thankyou:

Hi

I think you can use MD, but I’ll use letters of the alphabet so as to save some time.

Number of representatives in B ------- 1 box
Number of representatives in A ------- 1 box + 18
Number of representatives in C ------- 1 box + 18 + 6

School A
Boys: Girls------- 1A:3A

School B
Boys: Girls ------- 1B:5B

School C
Boys: Girls ------- 2C:5C

1A + 1B + 2C ------ 1p
3A + 5B + 2C ------3p

3A + 3B +6C ------- 3p

3A + 3B +6C ------- 3A + 5B + 2C

Hence, you’ll get 1C ------- 2B

Now change (2C + 5C) to 14B and do a comparison.

14B – 6B (1B+5B) ------- 24

8B ------- 24

B ------- 3

C ------- 6

Number of representatives in C ------- 7*6 ------ 42

Number of representatives in A ------- 42 - 6 ------ 36

Number of representatives in C ------- 18

Total number ------- 96

Best wishes

[tianzhu]

Treelodge:

Treelodge:

Please help to solve this Q :yikes: :?:

Q10 from Nanyang Prelim 2012. :gloomy:
Answer given = 266 2/3 m
:thankyou: :thankyou: :thankyou: [IMG]http://i49.tinypic.com/30nfdja.jpg\">

http://i49.tinypic.com/30nfdja.jpg\">

Hi

I did a quick check and get an answer of 266 and 2/3 (266.67)

I don't have time to prepare slide now, is the answer same at the ws?

Best wishes

[tianzhu]

Treelodge:

http://i50.tinypic.com/54yk9l.jpg\"> Some please help! :?: Need to double confirm answer to this Q.

Nanyang Prelim 2012 Q2.
:thankyou: :thankyou: :thankyou:

Hi

You would like to double confirm he answer.

My answer is 150.

Please share the answer given in the WS ?

Best wishes

[tianzhu]

Treelodge:

http://i48.tinypic.com/11t9wz6.jpg\"> Very pai seh! :imsorry: Another Q from Nanyang Prelim 2012. Q15. :gloomy: Someone please tell (lie to) me actual PSLE Maths is not that difficult.

How to do bi and bii? Answers given bi=21, 22, 51,52 bii=72
:thankyou: :thankyou: :thankyou: [img]

Hi

Could we have a clearer image, please?

Best wishes

[MathIzzzFun]

Treelodge:

http://i50.tinypic.com/54yk9l.jpg\"> Some please help! :?: Need to double confirm answer to this Q.

Nanyang Prelim 2012 Q2.
:thankyou: :thankyou: :thankyou:

area of shaded regions = 1/2 area of square = 1/2 x 10 x 10 = 50 cm²

ratio of shaded : unshaded --> 1: 3 = 50 : 150
Unshaded area --> 150 cm²

cheers.

[MathIzzzFun]

Treelodge:

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:?: Please help! :imdrowning:
Nanyang Prelim 2012 Q18 :slapshead:
Answer given = 96
:thankyou: :thankyou: :thankyou:

alternate approach using concept of multiples and a little Guess & Check..

School B, boys : girls --> 1 : 5 (total 6)
School A, boys : girls --> 1 : 3
School C, boys : girls --> 2 : 5
School A = School B + 18 = School B + 6 x 3
School C = School A + 6 = School B + 6 x 4
Total number of students in School B is a multiple of 6,
So, total number of students in School B is a multiple of 6 and total number of students in School C is also a multiple of 6

School C, boys : girls --> 2 : 5 --> 12 : 30
School A, boys : girls --> 1 : 4 --> 9 : 27 (6 less than C)
School B, boys : girls --> 1 : 5 --> 3 : 15 (18 less than A)
check --> boys: girls = (12+9+3) : (30+27+15) = 24:72= 1:3 √
So,
total number of students = 24 + 72 = 96

cheers.

[ksme]

[quote="kuts"]HI Ksme,


A B C D A A B B C C D D A A A B B B C C C D D D …? 160th
What is the 160th letter

Thanks in advance!


Hi,
Please see the solution below. It’s not a very elegant way but it gives the answer in a reasonable time. By the way, where is this question from and how many marks is the question for?

Pattern :
ABCD ------------------- 4 (1 time each alphabet in a set of 4)
AABBCCDD---------------- 8 (2 times each alphabet in the set of 4)
AAABBBCCCDDD----------- 12 (3 times each alphabet in the set of 4)
AAAABBBBCCCCDDDD ------ 16 (4 times each alphabet in the set of 4)
etc ------ 20 (5 times each alphabet in the set of 4)
etc ------ 24 (6 times each alphabet in the set of 4)
etc ------ 28 (7 times each alphabet in the set of 4)
etc ------ 32 (8 times each alphabet in the set of 4)
etc ------ 36 (9 times each alphabet in the set of 4)

Adding the total number of alphabets for each set to come close to 160 letters = 4+8+12+16+20+24+28+32= 144.

The 160th letter is therefore belonging to the 9 times each alphabet set of 4.

160-144 = 16

Since A will be shown 9 times (16-9 = 7), therefore, the 160th letter will be B.

Hope the above helps.

[MathIzzzFun]

Treelodge:

Treelodge:

Please help to solve this Q :yikes: :?:

Q10 from Nanyang Prelim 2012. :gloomy:
Answer given = 266 2/3 m
:thankyou: :thankyou: :thankyou: [IMG]http://i49.tinypic.com/30nfdja.jpg\">

http://i49.tinypic.com/30nfdja.jpg\">

Approach 1 --> using speed ratio = distance ratio

Tom's speed : John's speed = 160 : 200 --> 4 : 5
Divide the track into 18 units (=400m), so that each half is 9 units

At first meeting point, Tom would have run 4 units, John 5 units
From first meeting point to second meeting point, Tom would have run 8 units, John --> 10 units
From start to second meeting point, Tom ran --> 4 units+ 8 units = 12 units
Distance ran by Tom --> 12/18 x 400 m = 266 2/3 m

Approach 2 --> total distance /total speed concept

At first meeting point, total distance run by both = 400m/2 = 200m
From 1st meeting point to 2nd meeting point, total distance run by both = 400m
Total distance run by both from start to 2nd meeting point = 600 m
In 1 min, total distance run by both = (160m+200m)=360m
Time taken to cover 600m = 600/360= 5/3 min
In 5/3 min, distance run by Tom = 160 x 5/3 = 266 2/3 m

cheers.