Q&A - PSLE Math

[charsen]

Shimmer:

Hi, need help on this please. Thanks in adv.


Clare counted the number of 10cents, 20cents and 50cents in the bank. The no. Of 10cents was 17 more 50cents. After spending 60% of the 10cents, 25% of 20cents and 18 50cents, she had equal for all coins. The no. Of 50cents now formed 40% of not spent.

A) How many 10cents coin at first ?
B) How much spend in all ?

Hi
There is an error in the question.The error is in the last sentence.The sentence structure of the last sentence is something wrong.Make the nesscary changes to the last sentence.

[charsen]

xiaotiao:

Can anyone help me to solve this problem, thanks!!!


The average weight of a group of boys is 50kg. If one more boy who weighs 76 kg joins the group, the average of weight will become 52kg. Find the number of boys in the group.

Hopefully a kind soul can do me a favour.

Hi
Assume that the number of boys in the group before adding the 76kg boy is n.
Difference in average--->52-50=2kg
76-52=24kg
Always remember that the extra part,which is 24 kg of the boy is equal to the increase which is (2xn)kg.
N-24/2=12 boys
Total boys --->12+1=13 boys(ANS)
By right,i could have drawn a model to make it clearer,but due to time constrain,i could not do .
Hope this works
Cheers

[charsen]

ms_lim:

Can help to explain how to solve this question?


http://i47.tinypic.com/v4ov3b.jpg\">

b)
pattern no. no.of white tiles
2 8 --->8x1
4 32--->8x4
6 72--->8x9
8 128---->8x16

If you find the difference of white tiles between each pattern no.,2to4 is 24 4to6 is40,72 to 128 is 56.
Notice the part (1,4,9 and 25).these are square numbers.
So,Nth pattern no. is 8x(n/2xn/2)
8x(30/2x30/2)=1800(ANS)

[cimman]

Shimmer:

Hi, need help on this please. Thanks in adv.


Clare counted the number of 10cents, 20cents and 50cents in the bank. The no. Of 10cents was 17 more 50cents. After spending 60% of the 10cents, 25% of 20cents and 18 50cents, she had equal for all coins. The no. Of 50cents now formed 40% of not spent.

A) How many 10cents coin at first ?
B) How much spend in all ?

looks like Singlish has finally found it's way in to Maths Problem Sums. :faint:

[tianzhu]

Michaelia0816:

I want you to help me part (a) with the speed question as I dun understand and for the Ali question, which give me the answer, ( for checking)

Hi

I believe this is a typical Speed question from past years papers.

You can use the Speed Triangle, Distance ----- Speed*time and the relationship between the position of Ali and Steve.

To calculate the starting time taken by Steven, there is more than one option.

Best wishes

http://farm9.staticflickr.com/8301/7947589604_f3d0dc949b_z.jpg\">

[charsen]

ms_lim:

Can help to explain how to solve this question?


http://i47.tinypic.com/v4ov3b.jpg\">

C)
I try to find the general rule and i found it for how to find the total no.of tiles.It is (pattern no.x2-1)x(pattern no.x2-1)+4.
I subtracted 4 from the total no. of tiles in each question.For example,29-4=25.
You know that 25 is a square root of 5,which is a odd no.So,if you subtract 4 from all the total no. of tiles,you get the square root of odd no.Next,you should find the odd no. of the square root you found.
take pattern 3 as an example.
29-4=25
5x5=25
i need to find the relation ship between the pattern no. and the odd no.So,I used the formula to find odd numbers which is 2n-1-->(3+3)-1=5
And there,i found the formula.
Cheers

[charsen]

Winx5015:

Hi, anyone can help me with the following questions.


(1). A train left Station X with some commuters. At the first stop, no commuters alighted and the number of commuters who boarded the train was 1/5 of the original number of commuters in the train. At the second stop, 1/4 of the commuters alighted and 58 commuters boarded the train. At the third stop, 3/7 of the commuters boarded the train. At the last stop, all 315 commuters alighted. How many commuters were there when the train left Station x?

(2). Mother baked some square, round and oval cookies. For every 3 square cookies that were baked, 2 round cookies were baked. For every 4 square cookies that were baked, 3 oval cookies were baked.
(a). Find the ratio of the number of square cookies to round cookies to oval cookies baked.
(b). After mother baked another 120 round cookies, 30% of the cookies now were round cookies. How many square cookies did the bakery bake?

(3). Hadi had 295 more sweets than Ravi. After Hadi had given away 2/5 of the sweets he had and Ravi gave away 2/3 of the sweets he had, Hadi had 329 more sweets than Ravi. How many sweets did they have altogether at first?

Thank you

Hi
Q3.
At first: ravi-->15u Hadi--->15u+295


After :ravi--->5U Hadi---->9u+177
4U--->329-177=152
1U--->152/4=38
At first--->30u+295=(38x30)+295
=1495(ANS)

[charsen]

Winx5015:

http://i49.tinypic.com/zuse15.jpg\">


Can anyone tell me how to solve this question. Thanks

Hi
Is the shaded part quardrietlal QUTS?
cheers

[zanen]

hello can anyone help me wif this question? my fren sent it to me…Ken was climbing a flight of stair. While standing on a step, Ken realized that there were twice as many steps above he was step on,as there were below him. After ascending 8 more steps, he noticed that they were as many steps below him as they were above him. How many steps were there in the flight of stairs?

[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.