Tutor MathsGuru: Ask me for your burning Maths questions!

[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?

[Brenda10]

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, extracted from dd's working:

B:W
3:4
+70 : -112
8:7

B 21 490 + 896 (3x7, 70x7, 112x8)
W 32 (4x8)
----------------------
11u ----1386

1u -----126
3u ----378
4u ----504


378 + 70 + 48 + 504 = 1000

378 + 70 + 48 = 496

496/1000 x 100 = 49.6%

Answer: 49.6%

Hopefully the above help.

[TT2]

Dear Brenda10,


That's very impressive. But we are not able to understand the steps. :nailbite: Why multiply by 7 and 8? Could your dd help to enlighten us? Thank you once again.

B 21 490 + 896 (3x7, 70x7, 112x8)
W 32 (4x8)

[Brenda10]

TT2:

Dear Brenda10,


That's very impressive. But we are not able to understand the steps. :nailbite: Why multiply by 7 and 8? Could your dd help to enlighten us? Thank you once again.

B 21 490 + 896 (3x7, 70x7, 112x8)
W 32 (4x8)

Hi TT2,

DD is usng \"External Change\" Concept.

http://i55.tinypic.com/n13vx5.jpg\">

x7 and x8 are due to nothing remains constant and way to solve is make the end (parts, that is 8:7) the same by using the principle of common multiple. We can use the comparison to find the qty representing the different in unit (that is 3:4).

You may refer onsponge Book 5 (Pg 80) or Challenging Maths Problems Made Easy (Pg 82) for more detail explanation.

Sorry as we are not good in explanation.

[Maize]

MathIzzzFun:

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 !

[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.