Tutor MathsGuru: Ask me for your burning Maths questions!

[Joy]

Hi All,



Below is a math question from my dd, p5 sa1 exam.I also noticed similar question came out in another school for p6 sa1 this year.

Just wonder, anyone has seen similar question before?If yes, kindly advice where is the source?

Mdm Lek had 57 apples and oranges altogether.There were 3 fewer oranges than apples.She gave away half as many oranges as apples to her neighbours.vShe was left with twice as many oranges as apples.How many apples did she give away?

thank you.Regards
Joy

[Maths Monster]

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[Maths Monster]

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[corneyAmber]

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[corneyAmber]

http://i724.photobucket.com/albums/ww246/ks2me/P6Mathballs.jpg\">

[Joy]

Hi MM


This question actually is the last question of tao nan school p5 sa1 2010 paper and also from mee toh p6 paper this year.thanks a lot.

My girl actually used model to solve this problem.I know most in their school din get this correctly.

Am trying to find out where else can I find books that show similar concept.

Thanks again.

Maths Monster:

Joy:

Hi All,


Below is a math question from my dd, p5 sa1 exam.I also noticed similar question came out in another school for p6 sa1 this year.

Just wonder, anyone has seen similar question before?If yes, kindly advice where is the source?

Mdm Lek had 57 apples and oranges altogether.There were 3 fewer oranges than apples.She gave away half as many oranges as apples to her neighbours.vShe was left with twice as many oranges as apples.How many apples did she give away?

thank you.Regards
Joy

Total 57 apples and oranges and there were 3 fewer oranges than apples.
Number of apples = (57 + 3)/2 = 30
Number of oranges = (57 – 3) / 2 = 27

At end, She was left with twice as many oranges as apples

2 x (30 – 2u) = 27 – u
60 – 4u = 27 – u
3u = 33
U = 11

Therefore, apple given away = 2u = 22

Check:
At end:
Apple left = 30 – 22 = 8
Orange left = 27 – 11 = 16
Twice as many oranges as apples

Add - I think you are asking for this source of this problem. Not sure if there is a source but as this is quite a common problem of using ratio in a \"Before and After\" scenario. Hope this helps. Cheers, MM

[Maths Monster]

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[corneyAmber]

http://i724.photobucket.com/albums/ww246/ks2me/P6Mathmoney.jpg\">

[Vanilla Cake]

YLH88:

Hi Mathsguru and all maths experts,

Need your help with the below questions :

Hi YLH88,
I am not anyone close to be termed as a Maths expert but just a Sec 2 girl who has a younger sister taking PSLE Maths 2011.May I know where are your questions from? From your DS's 2010 P6 SA1 School Maths exam paper?

YLH88:

1) For time questions, is it true that the answer must be left in fraction and not decimal ? My DS wrote the answer as 37.5 h and the teacher marked him wrong. She said the answer should be 37 1/2 h. Thus, would like to check what is the practice for PSLE ? which is correct in PSLE context, 37.5 h or 37 1/2 h ?

Suggest that you write a letter to your DS's school Maths HOD to seek clarification in this matter. Otherwise, you may consider to write to http://moe.gov.sg/ or http://www.seab.gov.sg/index.html.Pls let readers of this forum know the outcome of your findings.

YLH88:

2) Sarah started driving from Town A to Town B at 4.30am travelling at constant speed.
James left Town A for Town B three hours later than Sarah travelling at a constant speed of 120 km/h.
When James arrived at Town B, Sarah was still 160 km away from Town B. Two hours later, Sarah reached Town B.
a) Calculate Sarah's average speed.
b) What time did James overtake Sarah ?

Since Sarah was still 160 km away from Town B and she reached Town B 2 hours later, average speed for Sarah = 160/2 = 80 km/h
(a) Sarah's average speed was 80 km/h.

Sarah got a 3 hour headstart (4.30 am against 7.30 am), so distance travelled = 80x3 = 240 km (80 km/h was Sarah's speed from a)

Difference in speed = (120-80) km/h = 40 km/h
240÷40 = 6 hours

Add 6 hours to 7.30 am will give 1.30 pm
(b) James overtook Sarah at 1.30 pm

YLH88:

3) Denise, Ginny and Florence each made some bookmarks for sale.At first, Denise had 1,365 bookmarks more than Ginny.Then Denise sold 420 bookmarks and made another 175 bookmarks.Florence sold 140 bookmarks and made another 350 bookmarks.Ginny made some more bookmarks and her number of bookmarks doubled.In the end, all the three girls had the same number of bookmarks.Find the total number of bookmarks the three girls had at first.

In the end
Denise: unit
Ginny: unit
Florence: unit

Before
Denise: unit+420-175 = unit+245
Ginny: unit÷2 = unit+245-1365 = unit-1120
Florence: unit+140-350 = unit-210

½unit = unit-1120 (Ginny)
½unit = 1120
unit = 2240

Before
Denise = unit+245 = 2240+245 = 2485
Ginny = unit-1120 = 2240-1120 = 1120
Florence = unit-210 = 2240-210 = 2030

2485+1120+2030 = 5635
Total number of bookmarks the three girls had at first was 5635.

YLH88:

4) The number of balls in Box A is 1/2 of the number of balls in Box B. 10% of the balls in Box A and 10% of the balls in Box B was moved to Box C.As a result, the number of balls in Box C increased by 20%.There are 72 balls in Box C now.How many balls were there in Box B at first ?

A : B
1u : 2u

1/10x1u = u/10
1/10x2u = u/5

Increase = u/10+u/5 = 3u/10

Original number of balls in Box C = 100/120x72 = 60
Increase = 72-60 = 12

3u/10=12
u = (12x10)÷3 = 40
2u = 40x2 = 80
At first,number of balls in Box B = 80

YLH88:

5) Andy. Weizhi and Peter had a total of $4582.After Andy had given 2/5 of his share to Weizhi, Weizhi then gave $55 to Peter.
As a result, the amount of money Peter had to the amount of money Andy had was in the ratio of 1 : 3.If Weizhi had $725 at first, find the amount of money Andy had at first.

Andy: 3/5 of (A)
Weizhi: 725+2/5 of (A)-55 = 2/5 of (A)+670
Peter: 1/5 of (A)

3/5 of (A)+2/5 of (A)+670+ 1/5 of (A)=4582
6/5 of (A) = 3912
A= 3912x5/6 = 3260
At first, amount of money that Andy had was $3260.

YLH88:

Thank you very much!!

You are welcome. It's still school holiday.Relax and enjoy a deserved break. Instead of obsessing about Maths, go out to participate in outdoor activities, enjoy fresh air and open spaces.PSLE 2010 Maths is on 7 Oct 2010 (Thu), still a long way to go.
:celebrate:

[YLH88]

Hi Vanilla Cake,


You are as helpful as any one of the parents in this forum even though you are only a sec 2 girl, besides managing your busying work schedule, you still help out alot in forum to solve these tough questions and I can tell that you care a lot for your younger sister. She is so lucky to have a big sister like you. May I know which school are you in if you don't mind saying ?
[quote]YLH88 wrote:
1) For time questions, is it true that the answer must be left in fraction and not decimal ? My DS wrote the answer as 37.5 h and the teacher marked him wrong. She said the answer should be 37 1/2 h. Thus, would like to check what is the practice for PSLE ? which is correct in PSLE context, 37.5 h or 37 1/2 h ? [/quote]Regarding the above, my DS's teacher is the HOD of Maths and she said she wanted the students to show the answer in fraction, not in decimal. I'm only concern if this also applies to PSLE. Guess I will check out with MOE and let all of you know in this forum.

Thank you so much for helping to solve the rest of the questions. I will try to 'digest' your solution. May need your help if I do not understand

Sorry, 1 more question below :

1) A box can either hold 180 bricks or 220 cubes.
When 108 bricks are in the box, what is the maximum number of cubes that can be put into the box ?

Btw, these questions are from his holiday homework worksheets, not from his SA1 paper. They are all super tought problem sums (in my opinion lah) ...