Tutor MathsGuru: Ask me for your burning Maths questions!

[Vanilla Cake]

Herbie:

thanks vanilla cake and maths guru for the providing the solutions.

Hi Herbie, you are most welcome.


Hi adhdadhd,
Thanks for your solutions and no worries about the small images.:D

Hi Mathsguru,
Thanks for your helpful and useful explanations.1 more question [5 marks] from http://www.orlesson.org/orp/09Ma/2009-Math-SA1-SCGS.pdf which needs your model solution. Today, I checked through your earlier solutions in the 85+ pages of this thread but could not find something similar to this one.

A coin box contained some twenty-cent and fifty-cent coins in the ratio 4 : 3. After 20 twenty-cent coins were taken out to exchange for fifty-cents coins of the same value and put back in the box, the ratio of the number of twenty-cents coins to the number of fifty-cents coins became 7 : 11. Find the sum of money in the box.

Thanks again for your kindness in helping us.
When you have time, it's good to have your own blog to group your Maths solutions by topics. This will help us to search and look out for similar questions with your worked solutions before contemplating to post our new questions. Just my 2 cents worth.

[Guan Hui]

20 x 20c>>> 8 x 50c


*note amount of money is always the same
for the 1st ratio 4:3
4x0.2+3x0.5=2.3(1 set of 1st ratio)
2nd ratio 7:11
7x 0.2 + 11x 0.5= 6.9(1 set of 2nd ratio)
since 1 set of the 1st ratio is 2.3 and 1 set of 2nd ratio is 6.9
1st ratio x 3
4:3=12:9
12:9 and 7:11 of 20c and 50c give the same amount of money.
But 12:9 must be able to give 20 20c and 8 50 c to become 7: 11

Using the 20c side
12-7=5(the 20c side of the ratio)
with the existing ratio, only able to give 5 20c coins.
we need 20… so,
20/5=4

Using the 50c side
11-9=2(the 50c side of the ratio)
with the existing ratio, only able to receive 2 50c coins.
we need 8… so,
8/2=4

(use either side is ok)
Using this we can know the sum of money = 6.9 x 4 = $27.60

Check
12:9=48:36(x4)
7:11=28:44(x4)
48-20=28
36+8=44
48x0.2+36x0.5=9.6+ 18 =$27.60
28 x 0.2+ 44 x 0.5= 5.6 + 22 = $27.60

[girlmum]

Hi Mathguru,


Pls help to draw the model for this P3 maths question:

1) Mrs Chan had 20 pencils. She gave each pupil 4 pencils.
a) How many pupils did she give the pencils to? Ans : 5
b) If each child broke 1 pencil, how many pencils were not
broken? Ans : 15

My DD2 knows how to do the number sentences but not the model. Pls assist. :?: Thanks.

[Guan Hui]

girlmum I did a video response for you I hope it helps=D

http://www.youtube.com/watch?v=TUB9r2i2v0g

[mathsguru]

Vanilla Cake:

Hi Mathsguru,

Thanks for your helpful and useful explanations.1 more question [5 marks] from http://www.orlesson.org/orp/09Ma/2009-Math-SA1-SCGS.pdf which needs your model solution. Today, I checked through your earlier solutions in the 85+ pages of this thread but could not find something similar to this one.

A coin box contained some twenty-cent and fifty-cent coins in the ratio 4 : 3. After 20 twenty-cent coins were taken out to exchange for fifty-cents coins of the same value and put back in the box, the ratio of the number of twenty-cents coins to the number of fifty-cents coins became 7 : 11. Find the sum of money in the box.

Thanks again for your kindness in helping us.
When you have time, it's good to have your own blog to group your Maths solutions by topics. This will help us to search and look out for similar questions with your worked solutions before contemplating to post our new questions. Just my 2 cents worth.

Hi Vanilla Cake,

Here are my solutions. I came up with 2 methods, but none of them involve models. Not all ratio questions require models to solve. With more practice, your sis will be able to identify which kind of solution suit which kind of question. Hope the solutions are clear enough for your sis!

And hope in near future, I'll be able to set up a blog like what you suggested. :politebleah:

Cheers,
MathsGuru

http://www.postimage.org/image.php?v=aVi98cA

http://www.postimage.org/image.php?v=aVi9aHJ

[mathsguru]

girlmum:

Hi Mathguru,


Pls help to draw the model for this P3 maths question:

1) Mrs Chan had 20 pencils. She gave each pupil 4 pencils.
a) How many pupils did she give the pencils to? Ans : 5
b) If each child broke 1 pencil, how many pencils were not
broken? Ans : 15

My DD2 knows how to do the number sentences but not the model. Pls assist. :?: Thanks.

Hi Girlmum,

Actually, number sentences are good enough for these questions as they are rather straightforward.

Although models are useful tools in solving questions, there's no need to draw models for every problem sum. Different problems require different methods of solving.

In any case, here's the diagrams. Hope your gal can understand these questions better after looking at the diagrams!

Cheers,
MathsGuru

http://www.postimage.org/image.php?v=PqwFu59

[girlmum]

Hi Mathsguru,


:thankyou: for your help.

[Hifive]

Hi Mathsguru


Need your help with the following questions:

1. At the beginning of a wedding banquet, there were twice as many female guests as male guests. After 40 female and 30 male guests left, the ratio of the remaining number of females to the remaining number of male guests were 9:4. How many more female than male guests attended the wedding?

2. In city A, every household has either one or two computers. The ratio of the number of households to the number of computers is 3: 5. What fraction of the household has only one computer?


Thanks in advance.

[mathsguru]

Hifive:

Hi Mathsguru


Need your help with the following questions:

1. At the beginning of a wedding banquet, there were twice as many female guests as male guests. After 40 female and 30 male guests left, the ratio of the remaining number of females to the remaining number of male guests were 9:4. How many more female than male guests attended the wedding?

2. In city A, every household has either one or two computers. The ratio of the number of households to the number of computers is 3: 5. What fraction of the household has only one computer?

Thanks in advance.

Hi Hifive,

Here are my solutions. Hope they can help!


MathsGuru

http://www.postimage.org/image.php?v=PqwTv4J

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

[starlight1968sg]

Hi mathsguru,

I need your help again.

Q1) Nathan is reading a book which has its pages numbered 1 to 150. What is the total number of digits used to number the pages?

Q2) Junwei’s watch was 1 minute faster while Junhong’s watch was 2 minutes slower every hour. At a certain time, both watches were reset to the correct time. At the same moment on the same day, Junwei’s watch showed 5pm while Junhong’s watch showed 4pm. What should the correct time be at that moment?

Q3) Lance answered 50 questions in a quiz. For each correct answer, 3 points were awarded. For each incorrect answer, 1 point was deducted. If he scored a total of 114 points, how many questions did Lance answer correctly?

The above questions are from p5 maths school worksheets.

MTIA.