Q&A - PSLE Math

[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]

[nounou]

Q15 part 1 http://i48.tinypic.com/1gmxiw.jpg\">

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

[nounou]

Q15 part 2. Uncle Tianzhu, you have lao hua ah? Can see clearly now? :rotflmao:

:thankyou: http://i50.tinypic.com/4rdqu9.jpg\">

Treelodge:

Q15 part 1 http://i48.tinypic.com/1gmxiw.jpg\">

tianzhu:

[quote=\"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

[/quote]

[nounou]

Dear MathzzFun and Tianzhu,


You are our saviour! :salute: 为人民服务！ :udaman:
:thankyou: :thankyou: :thankyou: :thankyou: :thankyou: :thankyou: :thankyou: :thankyou: :thankyou: :thankyou: http://i49.tinypic.com/2cd98nr.jpg\">

[MathIzzzFun]

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.

When the cyclist sees a bus, the next bus will be 15 minutes behind (**double double confirmed - not SMRT or SBS buses!).

Since the buses are travelling at 60km/h, so the next bus will be 15/60 x 60 = 15 km behind.

So, the bus takes 18 min to catch up 15 km,
15 km ÷ 18/60 = 50 km/h --> the bus is 50 km/h faster than the cyclist

cyclist's speed = (60-50) km/h = 10 km/h

cheers.

[tianzhu]

Treelodge:

Q15 part 2. Uncle Tianzhu, you have lao hua ah?

Hi

I've to admit I cannot resist the onslaught of old age.

Try to enlarge your images in the future so that we can see better.

The numbers on one side of a sheet adds up to 146.

bi ------21,22 and 51,52

146 – (1+2) ------143 (71 and 72)

Hence number of photos -------- 72

Best wishes