Level 3
A container holds some water up to a height of 71 cm. When 6 identical plastic balls are put into the container, the water level rises by 18 cm. One plastic ball is then removed from the tank, replaced by one metallic ball. The water level increases to 136 cm.

1. Find the ratio of the volume of 1 plastic ball to 1 metallic ball.
2. If the base area of the container is 150 cm², find the difference in the volume between the metallic ball and the plastic ball. Give the answer in cm³.

Level 3
Three cartons, A, B and C, contained 382 marbles. Hazel added some marbles into Carton A and the number of marbles in Carton A tripled. He took out half of the number of marbles from Carton B and added another 98 marbles into Carton C. As a result, the ratio of the number of marbles in Carton A, Carton B and Carton C became 6 : 2 : 9. What was the ratio of the number of marbles in Carton B to the total number of marbles in Carton A and Carton C at first? Give the answer in its lowest term.

Level 3
England and Thailand took part in Youth Games. From England, the ratio of the number of male supporters to the number of female supporters was 1 : 3. From Thailand, the ratio of the number of male supporters to the number of female supporters was 3 : 5. The total number of supporters from England was ²₅ the total number of supporters from Thailand.

1. What was the ratio of the number of male supporters from England to the total number of male supporters from both countries? Express the answer in the simplest form.
2. After 1956 male supporters from both countries left, the percentage of all the female supporters became 74%. How many more female supporters from Thailand than England were there at first?

Level 3
At a conference made up of speakers and participants, there were 10% more men than women. The ratio of the male speakers to female speakers was 8 : 5. There was an equal number of male and female participants.

1. Find the ratio of male speakers to male participants at the conference at first.
2. Halfway, 89 male participants left the conference and another 73 female participants joined the conference. In the end, there were ³₄ as many male participants as female participants remaining behind. How many speakers were there at the conference?