Tutor MathsGuru: Ask me for your burning Maths questions!

[Dharma]

Vanilla Cake:

free willy:

Box A has 200 red balls and 90 blue balls. Box B has 80 red balls and 100 blue balls. How many red balls and blue balls need to be moved from box A to Box B so that there are 80%of red balls in box A and 50% of blue balls in box B.

Hi free willy,

Your question is similar to RGPS P6 SA1 2009 P2 Q18 and the model solution had been provided by http://www.postimage.org/image.php?v=aVNZHuS on 22 Mar 2010.
Tang had also provided his http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&postdays=0&postorder=asc&start=1170 on 19 Mar 2010.

Using simultaneous equation to solve while waiting for Mathsguru's model solution.

Final scenario
Box A
Red balls : Blue balls
4 : 1 (80% : 20%)

Box B
Red balls : Blue balls
1 : 1 (50% : 50%)

4A+B = 200+80 = 280
A+B = 90+100 = 190

3A = 90
A = 30
B = 190-30=160

Final scenario
Box A
Red balls : Blue balls
120 : 30

Box B
Red balls : Blue balls
160 : 160

Before scenario
Box A
Red balls : Blue balls
200 : 90

Box B
Red balls : Blue balls
80 : 100

80 red balls and 60 blue balls to be moved from box A to Box B so that there are 80% of red balls in box A and 50% of blue balls in box B.

Hi Vanilla Cake,

Don’t you think the statement, “there are 80% of red balls in box A ….” is different from “80% of balls in Box A are red …..”

[Vanilla Cake]

Dharma:

Vanilla Cake:

[quote=\"free willy\"]Box A has 200 red balls and 90 blue balls. Box B has 80 red balls and 100 blue balls. How many red balls and blue balls need to be moved from box A to Box B so that there are 80%of red balls in box A and 50% of blue balls in box B.

Hi free willy,

Your question is similar to RGPS P6 SA1 2009 P2 Q18 and the model solution had been provided by http://www.postimage.org/image.php?v=aVNZHuS on 22 Mar 2010.
Tang had also provided his http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&postdays=0&postorder=asc&start=1170 on 19 Mar 2010.

Using simultaneous equation to solve while waiting for Mathsguru's model solution.

Final scenario
Box A
Red balls : Blue balls
4 : 1 (80% : 20%)

Box B
Red balls : Blue balls
1 : 1 (50% : 50%)

4A+B = 200+80 = 280
A+B = 90+100 = 190

3A = 90
A = 30
B = 190-30=160

Final scenario
Box A
Red balls : Blue balls
120 : 30

Box B
Red balls : Blue balls
160 : 160

Before scenario
Box A
Red balls : Blue balls
200 : 90

Box B
Red balls : Blue balls
80 : 100

80 red balls and 60 blue balls to be moved from box A to Box B so that there are 80% of red balls in box A and 50% of blue balls in box B.

Hi Vanilla Cake,
Don’t you think the statement, “there are 80% of red balls in box A ….” is different from “80% of balls in Box A are red …..” [/quote]Hi Dharma,
Thanks for your remainder.
Something is not right in the way this question is phrased.

free willy:

I don't know how to help my P6 boy with this homework question. He miss the class cause he had to go for tournment.

Hi free willy,
Pls clarify with your P6 boy about this homework question and let us know.
Thanks.

[Guan Hui]

free willy:

I don't know how to help my P6 boy with this homework question. He miss the class cause he had to go for tournment.


Box A has 200 red balls and 90 blue balls. Box B has 80 red balls and 100 blue balls. How many red balls and blue balls need to be moved from box A to Box B so that there are 80%of red balls in box A and 50% of blue balls in box B.

I think 80% of red balls mean 80 % of total red balls while 50 % of blue balls means 50% of total blue balls

200+80=280 red balls
80% of 280=224 red balls
90+100=190 blue balls
50% of 190=95 blue balls

For me, from my interpretation 24 red balls and 5 blue balls need to be move from box B to A..
I dunno if I am correct.>.< Just my opinion.
(I know question say how many balls from BOX A to BOX B)

[shemum]

Hi Maths Guru,


Please help me to solve the below question.

An MRT train was 2/5 full of passengers. At the first station, 1/2 of the passengers alighted and 17 people boarded the train. The train is now 1/4 full. How many passengers were there on the train at first?

Thank you.

Shemum

[verykiasu2010]

shemum:

Hi Maths Guru,


Please help me to solve the below question.

An MRT train was 2/5 full of passengers. At the first station, 1/2 of the passengers alighted and 17 people boarded the train. The train is now 1/4 full. How many passengers were there on the train at first?

Thank you.

Shemum

2/5 minus half = 1/5 = 0.2Full

0.2Full + 17 = 0.25F

hence 17 = 0.05Full

original number = 0.4Full = 8 x 0.05Full = 8x 17 = 136

should be easy with the model / diagram method too

[adhdadhd]

shemum:

Hi Maths Guru,


An MRT train was 2/5 full of passengers. At the first station, 1/2 of the passengers alighted and 17 people boarded the train. The train is now 1/4 full. How many passengers were there on the train at first?

Let me try:

Say, full train has 20 units.
2/5 full = 8 units.
1/2 alighted ==> 4 units alighted and left with 4 units.
17 people boarded ==> 4 units (left over) + 17
1/4 full = 5 units.
Thus, 1 unit = 17 passengers.
So MRT was originally 8 units = 136 passengers

Correct me if I am wrong.

[adhdadhd]

shemum:

Hi Maths Guru,


An MRT train was 2/5 full of passengers. At the first station, 1/2 of the passengers alighted and 17 people boarded the train. The train is now 1/4 full. How many passengers were there on the train at first?

Let me try:

Say, full train has 20 units.
2/5 full = 8 units.
1/2 alighted ==> 4 units alighted and left with 4 units.
17 people boarded ==> 4 units (left over) + 17
1/4 full = 5 units.
Thus, 1 unit = 17 passengers.
So MRT was originally 8 units = 136 passengers

Correct me if I am wrong.

[Guan Hui]

Solve using Percentage is easier to see for me=)

2/5=40%
1/2 left so remain=20%
+17 people=25%
so 5%=17 people
40%=17x8
=136 people^^



Both is correct moderators merge this with mathsguru thread?

[free willy]

thank you for all your help. The teacher has not gone through the question yet. I should have photocopy the Q, as such I can not verify the phrasing at this point. Nevertheless, the solution looks very logical. Is this methold called working backwards or internal transfer? [/quote]

[david59]

shemum:

Hi Maths Guru,


Please help me to solve the below question.

An MRT train was 2/5 full of passengers. At the first station, 1/2 of the passengers alighted and 17 people boarded the train. The train is now 1/4 full. How many passengers were there on the train at first?

Thank you.

Shemum

Using of model method, see attached
http://www.postimage.org/image.php?v=aVAM6fS