The third proportional to 38 and 15 is :

1. $\dfrac{15}{38 \times 38}$

2. $\dfrac{38 \times 38}{15}$

3. $\dfrac{15 \times 15}{38}$

4. $\dfrac{38 \times 15}{2}$

The third proportional to (x² − y²) and (x − y) is :

1. $\dfrac{x - y}{x + y}$

2. $\dfrac{x + y}{x - y}$

3. (x + y)

4. (x − y)

The mean proportion between 0.02 and 0.32 is :

1. 0.08

2. 0.16

3. 0.3

4. 0.34

The mean proportion between (3 + $\sqrt{2}$) and (12 − $\sqrt{32}$) is:

1. 6

2. $2\sqrt{7}$

3. $\sqrt{7}$

4. $\dfrac{15 - 3\sqrt{2}}{2}$