If the plane $$3x + y + 2z + 6 = 0$$ is parallel to the line $${{3x - 1} \over {2b}} = 3 - y = {{z - 1} \over a}$$, then the value of $$3a + 3b$$ is

Angle between the diagonals of a cube is

Consider the two lines

$${L_1}:{{x + 1} \over 3} = {{y + 2} \over 1} = {{z + 1} \over 2}$$ and $${L_2}:{{x - 2} \over 1} = {{y + 2} \over 2} = {{z - 3} \over 3}$$

The unit vector perpendicular to both the lines L₁ and L₂ is

The distance between the line $$r = 2\widehat i - 2\widehat j + 3\widehat k + \lambda (\widehat i - \widehat j + 4\widehat k)$$ and the plane $$a\,.\,(\widehat i + 5\widehat j + \widehat k) = 5$$ is