Q&A - PSLE Math

[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:

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

:?: 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.

[Zhu99]

ksme:

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.

A B C D --- 1 x 4
A A B B C C D D --- 2 x 4
A A A B B B C C C D D D --- 3 x 4

160/4 = 40 sets of 4

40 --- 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 4 [remainder of 4 sets]

4 x 4 = 16 letters left after (8 x 4) set

As next set is a set of 9, 16 - 9 (for 9 As) = 7 (the 7th B since it is less than 9).

The 160th letter is B.

[nounou]

My answer is also 150. :rahrah:

The WS answer is nonsense --> 100 cm2 = 10cm X 10cm :censored:
:thankyou:

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]

zanen:

can help wif this too?Tim, Shah and Raj had 216 book marks altogether. At first, Time gave 24 book marks to Shah. Then Shah gave 9 book marks to Raj. After that, Raj gave 17 book marks to Tim. The total number of book marks that Shah and Raj have now is half of what Tim has. The number of book marks that Shah has now is 3/5 of the number of book marks that Raj has. How many book marks did Time and Raj have altogether.

Hi

You may use “Work Backwards”.

Try to organise in a systematic flow, otherwise it may be confusing.

Does it refer to the beginning or the end? You may want to check with your source.

The answers for the end scenario are Tim ------ 144, Shah ------ 27 and Raj ------ 45.

Have a go at it.

Best wishes

[underthesea]

Please help.


Buses leave town A for town B every 15 minutes. A cyclist is on his way from town A to town B. The cyclist sees a bus every 18 minutes. If buses are traveling at a constant speed of 60 km/h, what is the speed (in km/h) of the cyclist.

[nounou]

Yes sir! :rahrah: :boogie:

tianzhu:

Treelodge:

[quote=\"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[/quote]