Q&A - PSLE Math

[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

[elkniwt]

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.

Hello,

May I know why is the area of shaded regions = 1/2 area of square ??? :?

Thanks!!!

[2DMommy]

Please help me with this question :


There was a total of 200 blue, red and green balls. There were twice as many red balls as blue balls. There were fewer green balls than red balls. The number of blue balls and red balls in each group was less than 100 and divisible by 3 and 4. How many green balls were there ?

[tianzhu]

2DMommy:

Please help me with this question :


There was a total of 200 blue, red and green balls. There were twice as many red balls as blue balls. There were fewer green balls than red balls. The number of blue balls and red balls in each group was less than 100 and divisible by 3 and 4. How many green balls were there ?

Hi

Red: Blue ------- 2:1

Numbers divisible by 3 and 4 are also divisible by 12.

So, find multiples of 12 which match the conditions.

Red ------ 96

Blue ------- 48

Green -------- 200 - 96 – 48 ------ 56

Best wishes

[tianzhu]

elkniwt:

May I know why is the area of shaded regions = 1/2 area of square ??? :?

Hi

The line FC divides the square ABDE into two rectangles of different sizes.

The underlying concept is a rectangle having the same base and height as a triangle has twice the area of the triangle.

Best wishes

[elkniwt]

tianzhu:

elkniwt:

May I know why is the area of shaded regions = 1/2 area of square ??? :?

Hi

The line FC divides the square ABDE into two rectangles of different sizes.

The underlying concept is a rectangle having the same base and height as a triangle has twice the area of the triangle.

Best wishes

Oh, I see!!! Thank you very much, Tianzhu!!! Thank you!!!
:thankyou:

[kiasuaunt]

tianzhu:

jonaandr:

3. There were 225 apples and 253 oranges in Box A.
There were 260 apples and 212 oranges in Box B.
Mr Chia moved some apples and oranges from Box B to Box A.
In the end, 40% of the fruits in Box A and 70% of the fruits in Box B were
appoes. How many fruits did Mr Chia move from Box B to Box A?

Hi

Q3 has been discussed before.

Please follow this link.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php&f=69&t=280&p=774807

Best wishes

Hi - I have the same question - sorry, I don't understand the solution. Is there another way of doing it ? Thank you.

[charsen]

kiasuaunt:

tianzhu:

[quote=\"jonaandr\"]
3. There were 225 apples and 253 oranges in Box A.
There were 260 apples and 212 oranges in Box B.
Mr Chia moved some apples and oranges from Box B to Box A.
In the end, 40% of the fruits in Box A and 70% of the fruits in Box B were
appoes. How many fruits did Mr Chia move from Box B to Box A?

Hi

Q3 has been discussed before.

Please follow this link.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php&f=69&t=280&p=774807

Best wishes

Hi - I have the same question - sorry, I don't understand the solution. Is there another way of doing it ? Thank you.[/quote]Hi
Basically,this question could be solved using the method called 'grouping method'.You can also do by units and parts,but grouping is safer and faster than units and parts.The key is that you have to group all the apples and oranges seperately and equate accordingly.
Cheers