If (3x - 9) : (5x + 4) is the triplicate ratio of 3 : 4, find the value of x.

If x, 2, 10 and y are in proportion, the values of x and y are respectively :

1. 0.2 and 0.25

2. 0.2 and 50

3. 0.4 and 50

4. 0.4 and 25

The mean proportion between $3 + 2\sqrt{2} \text{ and } 3 - 2\sqrt{2}$ is :

1. 1

2. -1

3. $2\sqrt{2}$

4. 3

If 2x, 9 and 18 are in continued proportion, the value of x is :

1. $2\dfrac{1}{4}$

2. $\dfrac{4}{9}$

3. 1

4. 9