Tutor MathsGuru: Ask me for your burning Maths questions!

[mathsnerd]

Grace has a container of red and white ribbons. If she adds in 10 red ribbons, 60% of the ribbons in the container are white. If she adds in another 30 white ribbons, 75% of the ribbons in the container are white. How many red ribbons are in the container?


I need a solution for this question please! :? :?:

[xxjustakidxx]

mathsnerd:

Grace has a container of red and white ribbons. If she adds in 10 red ribbons, 60% of the ribbons in the container are white. If she adds in another 30 white ribbons, 75% of the ribbons in the container are white. How many red ribbons are in the container?


I need a solution for this question please! :? :?:

Use ratio.

25% in 2nd situation = 40% in 1st situation.

[Vanilla Cake]

mathsnerd:

Grace has a container of red and white ribbons. If she adds in 10 red ribbons, 60% of the ribbons in the container are white. If she adds in another 30 white ribbons, 75% of the ribbons in the container are white. How many red ribbons are in the container?

Well, there are 10 red ribbons in the container. Let's leave this to Mathsguru to provide the solution.

[mathsguru]

mathsnerd:

Grace has a container of red and white ribbons. If she adds in 10 red ribbons, 60% of the ribbons in the container are white. If she adds in another 30 white ribbons, 75% of the ribbons in the container are white. How many red ribbons are in the container?


I need a solution for this question please! :? :?:

Hi Mathsnerd,

Here's my solution. Hope it's clear enough!


MathsGuru

http://www.postimage.org/image.php?v=gxUcCI0

[firebird]

Dear Mathsguru


Good morning.

Please, kindly,help me on some of the questions from Henry Park Primary School SA2 2009. Two of the questions contains diagrams, which I am unable to attach herewith using the PDF format. Very sorry for the inconvience caused. The quetions are:

1)Paper 1, booklet B, Question 16 : Write 3 thousands, 4 ones, 6 tenths and 18 hundredths as decimal.

2) Paper 1, booklet B, Question 19, with diagram :The diagram below is made of 4 semiclirles. The diameter of the biggest semicircle is 28 cm. Find the perimeter of the shaded figure. Express the answer in terms of pie.

3) Paper 1, booklet B, Question 21 : The average of 3 different odd numbers is 5. What is the largest possible value of one of the numbers?

4) Paper 1, booklet B, Question 29 : The ratio of the number of boys in the liabrary was 4: 5. After a group of boys entered the liabrary, 40% of the new total number of children were girls. What percentage increase in the number of boys?

5) Paper 2, Question 6 : Sharon bought M pens and 3 note books for $5. Each pen cost 40 cents. Express the cost of 1 notebook in terms of M.

6) Paper 2, Question 12, with diagram : Tank P was filled with water as shown in the diagram below. Water was then poured from Tank P to Tank Q until the height of the water level in Tank P became twice that of the water level in Tank Q. Find the volume of water in Tank Q. Give your answers in litres.

7) A librarian counted the number of adults in the library and found that 2/5 of the number of women was equal to 2 times the number of men. When another 12 men entered the library and 45 women left the library, the ratio of the number of women to men became 5:2.

b) Find the number of women at first.

Many thanks
firebird

[david59]

mathsnerd:

Grace has a container of red and white ribbons. If she adds in 10 red ribbons, 60% of the ribbons in the container are white. If she adds in another 30 white ribbons, 75% of the ribbons in the container are white. How many red ribbons are in the container?


I need a solution for this question please! :? :?:

Good day to you,

I would like to offer another way of using model to solve this question. Sorry for having to use hand-written illustration.

http://www.postimage.org/image.php?v=gx2r2gA

[Herbie]

Hi Maths Guru,


Can help to provide solution for the qn below:

Amy spent $320 of her income and saved the rest.
When she decreased her spending by 45%, her savings increased by 60%
How much was her income?

How to explain to the child that $320 is treated at 100% to work out the 45% decreased in spending?


Questions on percentage are quite confusing cos some times A+B = 100% and sometime A=100% and B= 100%. How to we tell which is which, when we read the qn? Can enlighten me?

Tx

[Guan Hui]

Total

100 percent

spent:save
$320:100%-320


new spent:new save
55%of 320: 160% of (100%-320)
176: 160%-512

176+ 160% -512=100%
60%=336
100%=$560

[Vanilla Cake]

Hi firebird,

http://www.orlesson.org/orp/09Ma/2009-P6-Math-SA2-HenryPark.pdf

Paper 1 Q16
Write 3 thousands, 4 ones, 6 tenths and 18 hundredths as decimal.

3000+4+6(0.1)+18(0.01)
3000+4+0.6+0.18
3004.78

Paper 1 Q19
The diagram below is made of 4 semicircles. The diameter of the biggest semicircle is 28 cm. Find the perimeter of the shaded figure. Express the answer in terms of ∏.

Perimeter of the shaded figure =½x∏x28 + ½x∏x28 = 28∏ cm

Paper 1 Q21
The average of 3 different odd numbers is 5. What is the largest possible value of one of the numbers?

Sum of 3 different odd numbers is 3x5 = 15
15 = 11+3+1
Largest possible value of one of the numbers is 11

Paper 1 Q29
The ratio of the number of girls to the number of boys in the library was 4: 5. After a group of boys entered the library, 40% of the new total number of children were girls. What percentage increase in the number of boys?

Before
B : G
5 : 4

After
B : G
6 : 4

Increase in terms of ratio for boys = 1 unit
Percentage increase in the number of boys = 1/5x100% = 20%

Paper 2 Q6
Sharon bought M pens and 3 note books for $5. Each pen cost 40 cents. Express the cost of 1 notebook in terms of M.

Cost of 1 notebook in terms of M = $(5-0.4M)/3

Paper 2 Q12
Tank P was filled with water as shown in the diagram below. Water was then poured from Tank P to Tank Q until the height of the water level in Tank P became twice that of the water level in Tank Q. Find the volume of water in Tank Q. Give your answers in litres.

Assume new height in Tank Q be H.
Volume of water in Tank P = 40x30x2H = 2400H cm³
Volume of water in Tank Q = 100x20xH = 2000H cm³

2400H+2000H = 55x40x30
4400H = 66000
H = 15 cm

Volume of water in Tank Q = 100x20x15 = 30000 cm³ = 30 litres

Paper 2 Q15
A librarian counted the number of adults in the library and found that 2/5 of the number of women was equal to 2 times the number of men. When another 12 men entered the library and 45 women left the library, the ratio of the number of women to men became 5:2.
a) What was the ratio of the number of women at first to the number of the men at first? Give your answer in its simplest form.
b) Find the number of women at first.

Before
Women : 5 units
2/5 of the women = 2/5x5 = 2 units
2 units of women is 2 times the number of men, so men would be 1 unit.

a) Ratio of the number of women at first to the number of the men at first = 5 : 1

Draw a model:
Men
[u][6][u][6]

Women
[u][6][u][6][u][6][u][6][u][6][45]

Shade the two blocks of [6] for men to represent 12 men due to enter the library to show the initial scenario. (Women : Men = 5 : 1)

(2 units)x5 = (5 units) + (6x5) + 45
10 units = 5 units + 30 + 45
15 units = 75
1 unit = 5

b) Number of women at first = 5 units +75 = 5(15)+75 = 75+75 = 150

Hope this helps while waiting for Mathsguru's detailed model solutions.

[Vanilla Cake]

Herbie:

Amy spent $320 of her income and saved the rest.

When she decreased her spending by 45%, her savings increased by 60%
How much was her income?

Before
Spent : $320 (100%)
Saving : ? (100%)

After
Spent : $176 (55%)
Saving : ? (160%)

$320+100% saving = $176+160%saving
60% saving = $144
100% saving = $240

Income = Spending+Saving
Before: Spent = $320 (100%) + Saving = $240 (100%) = $560
After: Spent = $176 (55%) + Saving = $384 (160%) = $560

Hope that I don't confuse you and let's wait for Mathsguru's solution.