Tutor MathsGuru: Ask me for your burning Maths questions!

[ck123]

Hi all


I need help with the model for this question.

The number of marbles in Box A, Box B and Box C was 195.
John added 60 marbles to those in Box A, doubled the number of marbles in Box B and halved the number of marbles in Box C.
The ratio of the number of marbles becomes 4:1:2.
What is the total number of marbles in the three boxes now?

Thanks

[Vanilla Cake]

Herbie:

Amy and Tommy each have some money. If Amy spends $50 per day and Tommy spends $60 per day, Amy would still have $500 left when Tommy has spent all his money.

If Amy spends $60 per day and Tommy spends $50 per day, Amy would still have $280 left when Tommy spent al his money. How much money does Tommy have?

Hi Herbie,
Your question is similar to this http://www.postimage.org/image.php?v=gxtwwpi which Mathsguru had provided clear explanations.

1st case
Amy : Tommy
5 : 6
25 : 30

2nd case
Amy : Tommy
6 : 5
36 : 30

Draw models for better visualisation,
1st case
Amy: 25 units + a long block to indicate $500 left
Tommy : 30 units

2nd case
Amy: 36 units + a long block to indicate $280 left
Tommy: 30 units

Make sure that total length of both blocks for Amy in 1st/2nd case must be the same.

25 units+$500=36 units+$280
11 units = $220
1 unit = $20

Tommy has 30 units = $600

Check
1st case - 10 days
Amy -> $1000-(10x$50) = $500
Tommy=> $600-(10x60) = 0

2nd case - 12 days
Amy -> $1000-(12x60) = $280
Tommy -> $600-(12x50) = 0

[Vanilla Cake]

Dharma:

Hi Vanilla Cake,


Your sister may wish to look at this while waiting for Mathsguru’s solution.

http://www.postimage.org/image.php?v=gxEDrbJ

Hi Dharma,
Thanks for your effort and time. Your alternative approach is the same method that I had taught her but she wants to learn the model solution by Mathsguru.

Hi Guan Hui/speedmaths.com,
Thanks for your solutions.

Hi Mathsguru,
From http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=6113&postdays=0&postorder=asc&start=100 and his http://chillycrab.webs.com/, is it possible for you to compile all your questions and solutions from this thread into a blog/website for others to learn from you?

[Vanilla Cake]

ck123:

I need help with the model for this question.


The number of marbles in Box A, Box B and Box C was 195.
John added 60 marbles to those in Box A, doubled the number of marbles in Box B and halved the number of marbles in Box C.
The ratio of the number of marbles becomes 4:1:2.
What is the total number of marbles in the three boxes now?

Hi ck123,
Thank you for posting this http://www.orlesson.org/orp/09Ma/2009-Math-SA1-RGS.pdf.My P5 younger sister also cannot understand the given worked solution.

While waiting for help, please see whether my method is useful or not?
Draw the model for \"after\" scenario:

After
Box A : 8 equal blocks
Box B : 2 equal blocks
Box C : 4 equal blocks

Before
Box A : 8 equal blocks - 60
Box B : 1 block
Box C : 8 equal blocks

8 blocks-60+1 block+8 blocks = 195
17 blocks = 255
1 block = 15

1 block is the same as 1 unit

Total marbles in the three boxes now : (8+2+4) blocks = 14 blocks
14 blocks = 14x15 = 210

Mod : Pls merge this thread with http://www.kiasuparents.com/kiasu/forum/viewtopic.php?p=160403#160403 so that Mathsguru can post a clear and well-illustrated model solution.

Thanks.

[OK Lor]

Dharma:

OK Lor:

Hi Mathsguru,


The product of two numbers, A and B, is 108. The difference betweeen A and B is a common factor of A and B. Find the values of A and B.

Thanks.

108 = 2 X 2 X 3 X 3 X 3 = 12 X 9
A = 12, B = 9 (A – B = 12- 9 = 3)
3 is a common factor of both 12 and 9.

Hi Dharma,

Thanks.

[Guan Hui]

The number of marbles in Box A, Box B and Box C was 195.

John added 60 marbles to those in Box A, doubled the number of marbles in Box B and halved the number of marbles in Box C.
The ratio of the number of marbles becomes 4:1:2.
What is the total number of marbles in the three boxes now?

final ratio
4u:1u:2u
initial
4u-60: 0.5u : 4u

4u-60 +0.5u +4u=8.5u-60
8.5u=195+60
8.5u=255
1u=30marbles

final ratio
4u+1u+2u=7u
7x30=210 marbles=D

[SoWoW]

Hi,


Please help to clarify!

Mrs Wong wants to pack 100 buns in boxes for her son to take to his class party. Each box can hold up to a max. of 8 buns. What is the minimum no. of boxes she will need to pack all the buns?

Should the answer be 12 or 13?
If the answer is 12, can help to explain why 12?

Thanks alot

[Dharma]

SoWoW:

Hi,


Please help to clarify!

Mrs Wong wants to pack 100 buns in boxes for her son to take to his class party. Each box can hold up to a max. of 8 buns. What is the minimum no. of boxes she will need to pack all the buns?

Should the answer be 12 or 13?
If the answer is 12, can help to explain why 12?

Thanks alot

Mrs Wong will need 13 boxes. She will pack 12 boxes with 8 buns each. The remaining 4 buns will be packed into another box. (12 + 1 = 13)

The answer cannot be 12 boxes, otherwise the remaining 4 buns will be left unpacked.

[SoWoW]

Dharma:

Mrs Wong will need 13 boxes. She will pack 12 boxes with 8 buns each. The remaining 4 buns will be packed into another box. (12 + 1 = 13)


The answer cannot be 12 boxes, otherwise the remaining 4 buns will be left unpacked.

Hi Dharma,

thank you so much. The answer provided is 12 so it's a wrong answer.
thanks for your clarifications. cheers

[Vanilla Cake]

Hi Mathsguru,

Could you pls help to post your approach to solve this 5-mark question from http://www.orlesson.org/orp/09Ma/2009-Math-SA1-AiTong.pdf?
There are workings for the solution but both of us (my P5 younger sister and myself)cannot understand them :oops:.Pls refer to page 27 of the PDF for the workings.

Devi had 26 more $5 notes than $10 notes. After paying $480 for a camera with some of the $5 notes, she had 6 times as many $10 notes as $5 notes.
a) How many $5 notes did Devi have at first?
b) How much money did Devi have left?

Could the model solution be applicable for such problem sum?
Thanks for your help.