1. Out of 40 000 people at a concert, 30% of the people were women, 10% of them were children and the rest were men. Some women left the concert with half the number of children before it ended. As a result ,the percentage of men increased to 75% of the number of the people left at the concert in the end .How many women were at the concert in the end?

2. Mr Raja has 3 cubical fish tanks of different size. The length of Tank A IS TWICE THE LENGTH OF TANK B and the length of Tank B is twice the length of Tank C. Mr Raja filled 20% of tank A, 35% of Tank B and 40% of Tank C with water at first .He then decided to pour all the water from Tank B and Tank c into Tank A. What percentage of Tank A is filled with water.

3. At first, 25% of Kumar's money was the same as 33.3% of Lily's money. Lily's father gave her $80, while Kumar spent $325. In the end, Lily had 2.5 as much money as Kumar.
a. How much money did Kumar had at first.
b. How much money did Lily have in the end.

The above questions were sent in from Vishnu ...

1. Out of 40 000 people at a concert, 30% of the people were women, 10% of them were children and the rest were men. Some women left the concert with half the number of children before it ended. As a result ,the percentage of men increased to 75% of the number of the people left at the concert in the end .How many women were at the concert in the end?


This question is from Raffles P5 2009 SA2

For the first question we can use the concept of External Unchanged where men remains the same before and after. Therefore make the units for men the same in the before and after ratios.



2. Mr Raja has 3 cubical fish tanks of different size. The length of Tank A IS TWICE THE LENGTH OF TANK B and the length of Tank B is twice the length of Tank C. Mr Raja filled 20% of tank A, 35% of Tank B and 40% of Tank C with water at first .He then decided to pour all the water from Tank B and Tank c into Tank A. What percentage of Tank A is filled with water.

This question is from Raffles P5 2009 SA2

For the second question, first calculate the capacity of each tank in units. The work through the percentages.



3. At first, 25% of Kumar's money was the same as 33.3% of Lily's money. Lily's father gave her $80, while Kumar spent $325. In the end, Lily had 2.5 as much money as Kumar.
a. How much money did Kumar had at first.
b. How much money did Lily have in the end.

The third question start with the Equal Fractions Concept so we can build a ratio. Then use External Change AKA Total Change to solve the rest.

Onsponge , I need your help in some more qustions .
Pls help me , and explain the answers in my e-mail .
I want to ask you some questions regarding percentage. Pls explain them using simple method and reply them to me on my email at the soonest as possible . Thank you!
% refers to percentage .
Take note of this symbol .

1.John has 90 more hens than ducks on his farm . 75% of his ducks and 20% of his hens were equal to 284 . How many hens were there on the farm ?

Ans : 370

2.60% of the beads in a box were blue . The rest were green . 840 blue bleads were taken out and the percentage of the green beads increased to 55% . How many green beads were there in the box ?

Ans :1232


3.Haley poured some water into a rectangular glass tank , 84cm long and 50 cm wide until it was fully filled . The height of the water decreased by 25% when Martin poured out 10.5 litres of water . How many litres of water did Haley pour in if there was a height of 4cm in the tank at first ?

Ans :25.2litre



4.There were 1800 pupils in a hall . After 15% of the girls and 20% of the boys left the hall , there were 1475 pupils left in the hall . How many more boys than girls were threr in the hall in the end .

Ans :285


5. Cindy gave Joyce 20% of her beads and the number of Joyce's beads increased by 0.5 of her original number . As a result , Cindy has 280 beads . How many beads did Joyce have in the end ?

Ans :210 .

Hi there,

Thanks for posting in the forum this time.

Another tip, is that you should try to start new threads for different questions. This will help speed up the process of getting solutions as many people in the community are willing to help out. It takes a considerable amount of time to respond to questions and to maintain a level of quality we rely on the community to help each other. For example, you can imagine that it takes 5 minutes to solve a problem and another 5 minutes to type it out so that you can make sense of it. In fact, some questions can take up to 15-20 minutes for a well drawn out solution. Thus for your 5 questions here, that could be more than 1 hour. So breaking it down will allow many ppl to spend 5 minutes each

With regards to emails, I believe Wendy has informed you that the fastest way to get responses is through the forum as there will be times, like this week, when the onSponge team is not available to respond to questions. I posted your original set of questions on your behalf to help you get started. Again, if you can imagine that all the ppl in this forum sent the questions through the email.... I think the result would be a heart attack Again, it's all about the community helping each other.

Thanks for your understanding

John has 90 more hens than ducks on his farm . 75% of his ducks and 20% of his hens were equal to 284 . How many hens were there on the farm ?

The concept here being used is Simultaneous Equations

1/5 hens + ¾ ducks --> 284
4/5 hens + 12/4ducks --> 284x4=1136

5/5 hens – 4/4 ducks --> 90
15/5hens – 12/4ducks --> 270

19/5hens --> 1136+270 = 1406
5/5hens --> 370

60% of the beads in a box were blue . The rest were green . 840 blue bleads were taken out and the percentage of the green beads increased to 55% . How many green beads were there in the box ?

Vishnu wrote:
3.Haley poured some water into a rectangular glass tank,84cm long and 50 cm wide until it was fully filled.The height of the water decreased by 25% when Martin poured out 10.5 litres of water.How many litres of water did Haley pour in if there was a height of 4 cm in the tank at first?
Assume the remaining height before pouring in the water into the tank be h cm

10.5 litres = 10500 cm³

84x50x(h+4)-10500=84x50x0.75(h+4)
4200h+16800-10500=3150h+12600
1050h=6300
h=6 cm

Amount of water that Haley poured in -> 6x84x50=25000 cm³ = 25.2 litres

Vishnu wrote:
4.There were 1800 pupils in a hall.After 15% of the girls and 20% of the boys left the hall , there were 1475 pupils left in the hall . How many more boys than girls were threr in the hall in the end.
Before
B+G=1800
Multiply by 0.8
0.8B+0.8G=1440 - (1)

After
0.8B+0.85G=1475 - (2)

(2)-(1)
0.05G=35
G=700
B=1800-700=1100

B-G (after)-> 0.8B-0.85G = 0.8(1100)-0.85(700) = 880-595=285
There were 285 more boys than girls in the hall in the end.

Vishnu wrote:
5. Cindy gave Joyce 20% of her beads and the number of Joyce's beads increased by 0.5 of her original number . As a result , Cindy has 280 beads . How many beads did Joyce have in the end?
Hmm.... this one is difficult for me to explain , so let me try while waiting for Chris Rogers' help :

Before
Cindy -> 100%

After
Cindy -> 80% ie 280 beads

80% -> 280
20% -> 280/80x20 = 70
70 beads given to Joyce.

Before
Joyce: u beads

After
Joyce: 1.5u beads

Increase -> 1.5u-u = 0.5u
0.5u-> 70 beads
1.5u -> 70/0.5x1.5=210 beads

In the end , Joyce had 210 beads.