$\sqrt{10} × \sqrt{15}$ is equal to

1. $6\sqrt{5}$
2. $5\sqrt{6}$
3. $\sqrt{25}$
4. $10\sqrt{5}$

$2\sqrt{3} + \sqrt{3}$ is equal to

1. $2\sqrt{6}$
2. 6
3. $3\sqrt{3}$
4. $4\sqrt{6}$

The number $(2 - \sqrt{3})^2$ is

1. a natural number
2. an integer
3. a rational number
4. an irrational number

If x is a positive rational number which is not a perfect square, then $-5\sqrt{x}$ is

1. a negative integer
2. an integer
3. a rational number
4. an irrational number