${n_1}:{n_2}:{n_3}::1:2:3$
$\because \frac{{{n_1}}}{{{n_2}}} = \frac{1}{2} = \frac{{{l_2}}}{{{l_1}}} \Rightarrow {l_2} = \frac{{{l_1}}}{2}$and $\frac{{{n_1}}}{{{n_3}}} = \frac{1}{3} = \frac{{{l_3}}}{{{l_1}}} \Rightarrow {l_3} = \frac{{{l_1}}}{3}$
$\therefore {l_1} + \frac{{{l_1}}}{2} + \frac{{{l_1}}}{3} = 110$ so ${l_1} = 60cm,{l_2} = 30cm,{l_3} = 20cm$

Statement$-2:$ Intensity of waves of given frequency in same medium is proportional to square of amplitude only.