Q&A - PSLE Math

[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

[kuts]

Hi,


Thanks a lot.

The question is from 2012 Pei Chuan Prelims and it carries two marks!

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.

[Zhu99]

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]225 + 260 = 485 --- No. of apples
253 + 212 = 465 --- No. of oranges

10 u -- Fruits in A
10 p -- Fruits in B

4 u + 7 p ---> 485 --- Apples

6 u + 3 p ---> 465 --- Oranges
2 u + 1 p ---> 465/3= 155
4 u + 2 p ---> 155 x 2 = 310

7 p - 2 p ---> 485 - 310
5 p ---> 175
10 p --> 175/5 x 10 = 350 --- No. of fruits in B at the end

260 + 212 = 472 --- No. of fruits in B in the beginning

472 - 350 = 122

Mr Chia moved 122 fruits from B to A.