If two lines $l$ and $m$ have equations $y = -x + 6$, and $y = -4x + 6$, what is the probability that a point randomly selected in the 1st quadrant and below $l$ will fall between $l$ and $m$? Express your answer as a decimal to the nearest hundredth.

[asy]
import cse5; import olympiad;
size(150);
add(grid(8,8));
draw((0,0)--(8,0),linewidth(1.2));
draw((0,0)--(0,8),linewidth(1.2));
label("$x$",(8,0),E);
label("$y$",(0,8),N);
draw((6,0)--(0,6)--(3/2,0));
label("$l$",(6,0)--(0,6),NE);
label("$m$",(0,6)--(3/2,0),NE);
[/asy]
We first find the areas of the triangles under $l$ and $m$ and in the first quadrant. From $l$'s equation, we find that at $x = 6$, $y = 0$. From $m$, we find that at $x = \frac{3}{2}$, we find that $y = 0$.

We then find the areas using the formula for a triangle: $\frac{1}{2}bh$. The area under $l$ is $\frac{1}{2}(6\times 6) = 18$. The area under $m$ is $\frac{1}{2}\left(\frac{3}{2}\times 6\right) = \frac{9}{2}$. Thus, the probability that the point selected will fall between $l$ and $m$ has probability $\frac{18 - \frac{9}{2}}{18} = \frac{27/2}{18} = \frac{3}{4} = 0.75$. Thus, the probability is $\boxed{0.75}$.