Tutor MathsGuru: Ask me for your burning Maths questions!

[MathIzzzFun]

Maize:

MathIzzzFun:

[quote=\"tinasen\"]Pls help with this question.

84 students appeared for a test. 1/8 of the girls and 4/5 of the boys passed the test. If a total of 24 students passed the test, find the number of girls failed the test.

Hi tinasen,

hope this helps

http://www.flickr.com/photos/62167097@N02/5920447017/in/photostream

cheers.

Hi
I was just trying out this questions and don't seem to understand.!!!
Also noticed that there was an error if I am not wrong -- there suppose to be 1/8 girls and 4/5 Boys but yr model is 1/8 boys and 4/5 girls!!
Please correct me if it is my mistake in understanding ![/quote]Hi

Oops..crossed eyes n misread the question.. the steps are the same though. I have made the corrections. Here's the updated solution..

http://www.flickr.com/photos/62167097@N02/5921483715/in/photostream

cheers.

[MathIzzzFun]

TT2:

Hi, please help in this maths qn... Thank you.


There were some blue marbles and white marbles in a bag. If 70 blue marbles were to be removed from the bag, the ratio of the number of blue marbles to the number of white marbles would be 3:4. If 112 white marbles were to be removed from the bag instead, the ratio of the no. of blue marbles to the no. of white marbles would be 8:7. When 48 more blue marbles were to be added into the bag, what percentage of all the marbles would be blue marbles at last?

hi

this was discussed earlier - http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=27&t=280&p=462495&hilit=There+were+some+blue+marbles#p462495

cheers.

[Andrew Lee]

In 2008, the enrolement of Jing Tao Primary School was 60% that of Shu Quan primary School. In 2009, 120 pupils left Shu Quan Primary School. In the end, the enrolment of Jing Tao Primary School was 80% that of Shu Quan Primary School in 2009. What was the enrolment of Jing Tao Primary School in 2009 ? :idea:

[Andrew Lee]

Yili, Lynn & Devi went shopping. Yili spent 0.25 of the total amount Lynn and Devi spent, while Devi spent 4/11 of the total amount Yili and Lynn spend. Lynn spent $37.50 more than Yili. If Lynn had $90 before she went shopping, what fraction of her money did she spend? express your anser in its simplest form. :imdrowning:

[MathIzzzFun]

Andrew Lee:

In 2008, the enrolement of Jing Tao Primary School was 60% that of Shu Quan primary School. In 2009, 120 pupils left Shu Quan Primary School. In the end, the enrolment of Jing Tao Primary School was 80% that of Shu Quan Primary School in 2009. What was the enrolment of Jing Tao Primary School in 2009 ? :idea:

Hi

Number of pupils in Jing Tao remained the same in 2008 and 2009.

In 2008, ratio of pupils in Jin Tao : Shu Quan = 3 : 5 = 12u : 20u
In 2009, ratio of pupils in Jin Tao : Shu Quan = 4 : 5 = 12u : 15u
So 20u -15u = 120, 5u = 120, 1u = 24

In 2009, number of pupils in Jin Tao = 12u = 12 x 24 = 288

cheers.

[MathIzzzFun]

Andrew Lee:

Yili, Lynn & Devi went shopping. Yili spent 0.25 of the total amount Lynn and Devi spent, while Devi spent 4/11 of the total amount Yili and Lynn spend. Lynn spent $37.50 more than Yili. If Lynn had $90 before she went shopping, what fraction of her money did she spend? express your anser in its simplest form. :imdrowning:

Hi

Ratio of spending, Yili : Lynn+Devi+Yili = 1 : 5 = 3u : 15u
Ratio of spending, Devi: Lynn+Devi+Yili = 4 : 15 = 4u : 15u
Ratio of spending Yili : Devil : Lynn = 3u : 4u : (15u-3u-4u) = 3u : 4u : 8u

so 8u - 3u = $37.50, 5u = $37.50, 1u = $7.50

Lynn spent 8u = 8 x $7.50 = $60
Lynn's spending as a fraction of her money = 60/90 = 2/3

cheers.

[tinasen]

I couldn't understand why 1/8 of girls is equated to 4/5 of boys. Also instead of making the number of units 40 for boys and girls (taking the LCM of 8, 5), why each unit is divided into 4 instead. Sorry if it's a simple one. I'm trying my best to explain my DS with the solution.

Thanks
Tinasen

Hi

Oops..crossed eyes n misread the question.. the steps are the same though. I have made the corrections. Here's the updated solution..

http://www.flickr.com/photos/62167097@N02/5921483715/in/photostream

cheers.[/quote]

[TT2]

Hi Brenda10 & MathIzzzfun,


Thanks for your help. It is better now. Sometimes doing the questions made me feel so silly … haiz. I was pondering over it for over 2 hrs!

[MathIzzzFun]

tinasen:

I couldn't understand why 1/8 of girls is equated to 4/5 of boys. Also instead of making the number of units 40 for boys and girls (taking the LCM of 8, 5), why each unit is divided into 4 instead. Sorry if it's a simple one. I'm trying my best to explain my DS with the solution.

Thanks
Tinasen

Hi

Oops..crossed eyes n misread the question.. the steps are the same though. I have made the corrections. Here's the updated solution..

http://www.flickr.com/photos/62167097@N02/5921483715/in/photostream

cheers.

[/quote]

Hi

1/8 of girls was not equated to 4/5 of boys.

1/8 = 4/32

This is what the model show in pictorial form:

4/32 of girls + 4/5 boys = 24
So, 1/32 of girls + 1/5 boys = 24 /4 = 6 ---- (A)

5/32 of girls + 5/5 of boys = 24 + 6 = 30
Total girls and boys
= 32/32 of girls + 5/5 of boys
= 27/32 of girls + 5/32 of girls + 5/5 of boys
= 27/32 of girls + 30
= 84

27/32 of girls = 84 - 30 = 54
1/32 of girls = 54/27 = 2

Number of girls who failed = 28/32 of the girls = 28 x 2 = 56

cheers.

[tinasen]

Thank you very much. Now it is very clear.

I got it. Thanks a ton.
- Tina

MathIzzzFun:

tinasen:

I couldn't understand why 1/8 of girls is equated to 4/5 of boys. Also instead of making the number of units 40 for boys and girls (taking the LCM of 8, 5), why each unit is divided into 4 instead. Sorry if it's a simple one. I'm trying my best to explain my DS with the solution.
Thanks
Tinasen

Hi

Oops..crossed eyes n misread the question.. the steps are the same though. I have made the corrections. Here's the updated solution..

http://www.flickr.com/photos/62167097@N02/5921483715/in/photostream

cheers.

Hi

1/8 of girls was not equated to 4/5 of boys.

1/8 = 4/32

This is what the model show in pictorial form:

4/32 of girls + 4/5 boys = 24
So, 1/32 of girls + 1/5 boys = 24 /4 = 6 ---- (A)

5/32 of girls + 5/5 of boys = 24 + 6 = 30
Total girls and boys
= 32/32 of girls + 5/5 of boys
= 27/32 of girls + 5/32 of girls + 5/5 of boys
= 27/32 of girls + 30
= 84

27/32 of girls = 84 - 30 = 54
1/32 of girls = 54/27 = 2

Number of girls who failed = 28/32 of the girls = 28 x 2 = 56

cheers.[/quote]